San Francisco is a really cool city. I definitely like it there. I wish I were the one going - I'd love to go back.

But anyway, Haight Ashbury, Castro and The Mission are all very much worth checking out. As for things like the Fisherman's Wharf... meh. Not really that interesting. At all.
San Francisco is great for just randomly walking around and exploring. The Mission and around e.g. has a hell of a lot of cool and pretty murials.

As for accommodation the only place I know is a hostel in The Mission because that's where I stayed. I don't even remember the name, but it was cheap.

Oh, and be sure to go to Zeitgeist. It's a really great bar not far from The Mission.