Lots of great things to do in the city. You can rent a GoCar, do a Duck tour, hit up Alcatraz, etc. The Ferry building is cool. Lots of great little food places there. Chris Cosentino has a Salumeria there. They also have a farmers market there that is cool to cruise around.
Also, Bobos is probably the best steak that I have had in the city: http://www.boboquivaris.com/