Congrats on your acceptance...I've been accepted for the photo post-bacc but I haven't decided where I'll be going.
I lived in San Francisco last year. If you'll be depending on public transportation to get around, try utilizing the Bay Area public transit website, 511.org, as you're looking for places on Craigslist so you can see how long it will take for you to get to school. Looking for a place in Berkeley or Oakland that's close to BART will take you right into SF in no time, even faster than if you live in the outer parts of SF.
If you can afford a couple of weeks in a weekly rate hotel, I would recommend grabbing a room in downtown SF around Union Square or Nob Hill and explore SF, Berkeley and Oakland to really get a feel for what neighborhood you like. There really is something for everyone but I don't know what your standard of living and budget details are so that's what I would recommend.
If you offer more specifics, you'll definitely get more advice!