I lived in SF and Oakland about 15 years, and I've been to almost all of the places mentioned. I especially like nature, so give two thumbs up to the suggestions to go up north, but that will take a lot of driving, and you should go for more than two days. Same goes for Yosemite. Also there's Fort Ross up north. You can drive around in the hills above Oak/Berk. There's a nice park up there that used to have live steam trains you could ride in. The Marin headlands has a nice road running along somewhere after you cross the bridge; I think it's US 1. Santa Cruz beach and boardwalk is also a fun place. If you get homesick, you might take in a concert by Slavyanka, a men's chorus based in SF.