Eva,
As an SF native transplanted to Stockholm, I wish you a good trip. You could spend a lifetime shooting on the streets of San Francisco, but if you have the chance to rent a car, a trip down the coast to Monterey/Pacific Grove/Carmel would definitely be in order. If you make it down there, a pilgrimage to Point Lobos is definitely worth it, if only to walk in some famous footsteps (i.e. Adams, Weston et al) and enjoy the nature.
Trevlig resa!
Steve