2010/1/27 phoebe ayers phoebe.ayers@gmail.com:
I researched this question out of curiousity last year, and the most promising venue seemed like UC Berkeley, with their blocks of dorms that they rent out for conferences. USF/SF State similarly have space. Someplace like Mission Bay is gorgeous but pricey.
Phoebe, did you look at Fort Mason? They've got a beautiful space, a nonprofit rate, and there are places to eat and stay close by. Transportation is not the best, though. It doesn't have that collegial residency nearby, though, a feature that's been great at previous Wikimanias.
=Eugene