I visited Napa to see family, but as sadi above, if you don't like wine, it's pretty much just miles and miles of vineyards. We did cut up through there and then came back down the pacific highway, which was stunning. South of San Francisco is pretty much just urban sprawl, so I'd recommend a day trip up the coast/across the bay and spend the rest in the city. Alcatraz is worth a visit. Coit tower is good for the views. Theres a dive bar by the name of Black Magic Voodoo Lounge on the corner of Van Ness and Lombard which is worth a visit if you are in the area. The subs just down the road are good too. Fishermans Wharf is your standard tourist fare. Take the cable cars down into Market and Castro for a look around., If you go to civic square, dont wander onto the streets behind Macys unless you want ganged by tramps.