First. That's a great deal and it seems like you could have escaped which is your #1 priority. However, lets go with the thought that the fight is not escapable so you can cover the "getting jumped by a group of douchebags" moment.
I have been jumped maybe 10+ times in my life and I am going to tell you this. If more than 1 person is standing around trying to kick me. I instantly feel that my life is in danger and I will attempt in all ways to kill them. That is now my #1 priority.
Because you CAN die from having someone kick you in the face or neck, or stomach while on the ground. My cousin is paralyzed from being kicked in the back of the head when he was jumped by only 2 people.
If you are on the ground getting kicked, you damn well better try to kick and punch at balls, breaks legs(you can do this by trapping a leg against your body and rolling into or sideways against the knee), break ankles by kicking out at the spot a couple inches above the ankle, and frankly do everything you can to end their life or make them no longer willing to fight. I mean full on neutering of them. You do everything you can in your power to get away and get standing.
The moment you are standing you can move Priority 1 to "running the fuck away if possible"
Now if you are not on the ground and in a normal standing fight. Some boxing classes can do wonders but unlike others who say it will teach you a good couple punches, more importantly it will teach you;
1 Footwork (this allows you to learn how to stay on your feet, make clear decisions and leave)
2 Defense (this allows you to duck, weave, not get punched in your fool head.
Then way below importance is punching as you can't deliver damage if you are on the ground or have your head pummeled.
It is a dangerous thing getting in a fight but being jumped or being tackled and dropped to the ground is even more dangerous. You HAVE to do everything you can to get off the ground. IMHO.
My theory for curling up and just letting them kick you.
This can indeed work. It can work well but it is taking a fucking freakish chance.