Weirdly, SF is, now I've been to NY, the American city I most want to visit. It doesn't have the same mystique for me that NY had/has, but I've never been to the West Coast and really want to compare it with cities in the East and Midwest that I've been to. I don't drive so LA seems out of the question, but from what I know about SF it's a fairly walkable city.
The only thing that puts me off is that I've only ever properly met one person from there in my life, and he was possibly the biggest, most pretentious arsehole I've ever encountered. Every cliche about Haight-Ashbury flakiness was totally crystalised in this tie-dye wearing Grateful Dead obssessive who, despite being only in his mid twenties, appeared to be completely unaware of any cultural development post 1968. I know you can't judge a place by one person, but this guy had such a negative effect on me that he made me question whether I could deal with the possibility of encountering more people like him. I'm guessing that as long as I avoided the Haight-Ashbury district, I'm not that likely to meet those type of walking cliches while I'm there.
Besides, Dirty Harry and the Zodiac Killer came from there, so they can't all be like him ... can they?
"Go ahead Dead-head, make my day!"