As someone who just lived through essentially a direct hit from the dirty side of Irma when she was still a 170mph beast, here's some advice for my Puerto Rico brothers:
Choosing where to stay
Irma hit the hell out of us with winds of 150mph (we dodged the eye by 30 miles but it was a huge storm and we caught the bad side). However, very, very few concrete buildings were destroyed. Don't let the images of those few buildings that lose walls scare you - you're safe in a concrete building constructed in the last 20 years. So make sure you are in a concrete building, and make sure your windows are boarded up. If not, search for a shelter or stay with a neighbour. If you have family living in a wooden or otherwise insecure building, strongly encourage them to stay with you.
If you are in an area that typically floods or is at sea level and prone to storm surge, make sure you have a second floor you can get to. If you don't feel like your roof is secure, make sure you have a basement or some room not covered by the main roof.
During the storm, stay away from exposed (unboarded) windows. Ensure that you have a room with no windows that you can go to if the windows come in - this will typically be a bathroom. Bathrooms saved many people here when a window blew out, a roof came off or a wall collapsed.
Keep some supplies in your escape room as you may be forced to flee there quickly. For us, we fled the apartment into the apartment building stairwell when it appeared the glass doors were going to come in. We already had secondary supplies, blankets and mattresses in the stairwell so this wasn't as bad as it could be. Had we not done this, we would have been moving heavy coolers during evacuation (dangerous) or been less likely to move (dangerous) or stuck without water from 8.30pm to 4am when we were in the stairwell (not good, not fun).
Supplies and water
However much water you typically use per day, triple it for your supplies per day you expect to be without water. This is because you will be busting your ass repairing things, lifting things, and moving around a lot by foot. In Caribbean heat, you will sweat out water at an amazing rate. So make sure you have triple the water you'd use, daily, per person, for a week.
You need a cooler or multiple to store the water. Freeze it before you put it in the cooler, then add ice. This combo will keep the water frozen for up to 48 hours, and yet it'll defrost in just an hour if you need a drink. If you don't freeze the water and just add ice you'll last just 12 hours or so by comparison. Don't mess with your cooler once it's closed, leave it closed. Add some cheap meats that you wouldn't mind spoiling if they do. Frozen sliced bread is a great addition as it thaws quickly and is full of calories. Add some chocolate as that's also a great calorie boost if you're working and can improve mood and morale, especially with kids.
Being ready on time
A lot of people look at when the hurricane is due to arrive. This is a mistake - you need to be hunkered in 3 hours before tropical storm force winds are due to arrive. You will have emergencies that need to be dealt with at the very end so make sure you give yourself those three hours. Once tropical storm force winds hit, it's too late too do much of anything. Irma arrived on us quicker than we could possibly have anticipated - the hurricane was due to hit at 11pm - by 11am (12 hours beforehand) it was too late to do anything of worth. We had planned to be ready by 2pm - in the end that was a way optimistic decision but fortunately we got up early on the day and were ready literally just in time.
Don't leave anything late. Be ready at least 12 hours in advance of when the eye is due to hit you. That looks like 8pm tonight as a deadline for being ready in PR.
Power and Light
You will be without power for a while. Prepare for it. The most important device you will need to power is your phone, for communication's sake. Losing power to your phone is isolating and devastating. The single best and most consistent battery you have is your car. Therefore make sure you have a car charger for your phone. If you don't, you will deeply regret it. If you can get your hands on a power pack for your phone, all the better, but that's only a couple of charges. Your car could get you through the week.
Do NOT waste all your power on social media during the storm! Leave at least 15% battery to call immediate family the next morning or feel like an idiot, your call.
As for lights, I got a pack of these LEDs you stick to the wall and they were perfect during the week we had without power. Put them in crucial areas like your entrance, stairs (dangerous without lights), bathroom and bedroom. You will get used to where they are like light switches and won't need to fumble around in the dark. If these areas are lit, even dimly, that's enough for someone to find a lighter and candle and get the room properly lit. You need multiple flashlights. Leave at least one in your car so you always have one wherever you go.
Get an LED lantern to carry with you in your house - safer than a gas latern but handier than a flashlight. Have enough batteries to power everything for a week. Have at least two candles per room but make sure you don't leave them lit when you're not using that room - in general LED lighting is much safer than fire and I used it a lot more.
Cooking
Barbecues are crucial here. If you have one, make sure you're stocked with gas or charcoal. If you don't have one, find a neighbour who does. Then buy charcoal or a gas canister so that if you need to use it, you won't be using their resources. This is the difference between a neighbour letting you use their shit and not. Trust me, two days after the storm if everyone else is eating cold tinned beans and you're barbecuing your sausages and chicken from your cooler you will feel like a king.
If you do have a barbecue and plenty of fuel, consider setting it up outside after the storm with a sign saying 'bring your own food'. Many people did this here and it's huge for those without the ability to cook after a storm.
Parking your car
A lot of people here suffered damage to their car from projectiles or falling trees. Parking your car somewhere safe is hugely important as you'll need it massively after the storm.
You need it within 10 minutes walking distance for after the storm, but don't worry if flooding would make it inaccessible - if the flooding is that bad your car would be of no use anyway. Make sure it's not somewhere prone to flooding - many underground car parks are. Make sure there are no tall trees around. Preferably park in an office space surrounded on 3 sides with building with no loose debris around and no trees about. I live at sea level so I parked my car snug against an office wall 15 minutes walk up a hill - it was worth the walk after the storm to know my car was safe during it.
Obviously make sure every single car you have access to have a full tank, and if petrol is rationed (it will be) avoid making unnecessary journeys after the storm.
Air Conditioning
Prepare to be without it for a long time if you had it to start with, BUT... once again your car will be a lifesaver. If you have small infants who are cranky and overheating, even half an hour in your car's AC as you do errands can make all the difference. It can be a half-hour of calm in what'll be a super-stressful environment. Blast the AC while the car is running, then keep the car doors closed once your done with the errands and enjoy it.
Neighbours
Get the phone numbers of all your neighbours. This isn't so much for during the storm as it is to check on them afterwards and band together to repair your property. One person can't do much on their own, a group of 10 neighbours can start clearing debris very quickly. It's also a great way to get to know neighbours you never even knew you had which is a bonus.
Dealing with irrational people
You're going to have to deal with family members and neighbours who are deeply stressed and in many cases making poor decisions. Don't snap at them - don't make a tense situation worse. Let people vent if they have to. Where to put your foot down is where people are making decisions concerning your own safety, but even there you need to do so politely and without confrontation. The storm will pass, don't let it screw up your closest relationships in the couple of days it'll affect you.
If someone wants to evacuate outside or open a door or window during the storm - don't let them if it'll affect you. If you feel secure where you are but a family member wants to go to a shelter you don't feel is secure - let them go but don't feel like you have to go with them - your own safety and peace of mind is paramount.
Senior people and mothers of infants will probably be the most stressed so be aware that they may need some space. We had a young mom with us who was duct-taping her baby to her in the middle of the storm - rationality can go out the window when things are at their worst.
After the storm
Adrenaline will still be high right after the storm - use this to clear the worst debris, get your things back together and formulate a plan for riding out the next couple of days. If you leave this you will find that people have become scattered, making planning more difficult, and that exhaustion has set in, making moving things difficult. Right after the storm is the best time to get into action and get things done.
Once your place is secure, your car is secure, and your supplies are secure, then start calling people and letting them know you're okay. Then see if anyone else needs help. There will be days of work to do.
Good luck guys. You'll be fine, it's just very nerve-wracking and a ton of work both before and after the storm.