You should definitely go to Java Beach Cafe in the evening.
The cafe is basically on the beach. I used to go there to grab a sandwich, watch the sunset and chill on the beach.
Yeah, it gets cold at night sometimes.
My dad used to tell me about how he has burned out so many clutches on the cars he was learning manual on.
Anyways, understand that San Francisco is a puny part of the Bay Area. If you want a nature retreat, as some have said, you should go across the bridge towards Marin county and go to Muir Woods. You get to see the massive redwood trees that have been there for more years and I can count out loud. I did a hike up to the top of Muir Woods it was probably one of the more memorable things I've done in California. The drive there is also very awesome.
The sunset is amazing from there as well.