There's tons of stuff to do in the city and the surrounding area, you've gotten some good ideas already, i'll add a few:
Golden Gate Bridge/Fort Point/Marin Headlands - Underneath the Golden Gate is Fort Point, an old fort guarding the entrance to the Bay. Interesting views, and often you can find surfers here. Walk across the Bridge, or drive across and up the hill on the other side to get spectacular views of the Golden Gate with San Francisco in the background.
Napa/Sonoma Wine country - less than an hour north of San Francisco is the wine country. Drive up and do some tasting, or get with an organized group so that there is more tasting, and less driving!
Monterey/Santa Cruz - Take a couple hours and drive down the Pacific Coast Hwy 1 to the Monterey Peninsula. Amazing views all along the coastline, as well as 17 mile drive in Monterey. One of the best Aquariums in the world is in Monterey, and well worth a visit. Or stop at any one of the numerous beaches you'll pass on the way down.
Yosemite - Might still be a bit too snowy up there, but you can get to Yosemite in about 4 hours. Could easily do a long day trip if you desired. Again well worth it to drive up and see the Valley and walk around if you can.
The 4th & Mission Marriott Hotel Bar - Has a spectacular bar at the top of the hotel, with 360 views of the entire city and area. Drinks are expensive, but well worth it to go around sunset and enjoy the changing landscape, and emergent city lights.
Pier 39/Fishermans Wharf/Alcatraz - Very touristy area, but for good reason, its cool! Lots of shops, restaurants, ferries, bay cruizes. A boat dock taken over by Sea Lions. Alcatraz is well worth seeing.
Music - There are tons of small venues all over the city. Blues/Jazz, you can find pretty much anythign in the city. Pick up a free San Francisco Bay Guardian from the street (Weekly on Wednesday) for listings of all the happenings durning the week in the city.
North Beach - Italian section of town with lots of good restaurants (right next to china town too).
Those are some additional ideas. There really is limitless stuff to do in the city and area, something for every taste! Enjoy your vacation!
What, you ask, was the beginning of it all?
And it is this...
Existence that multiplied itself
For sheer delight of being
And plunged into numberless trillions of forms
So that it might
Find
Itself
Innumerably.
-Sri Aubobindo
Saidin is a fictional character, and only exists in the collective unconscious. Therefore, we both do and do not exist. Everything is made up as we go along, and none of it is real.