Also, one of the premier music festivals in the United States will be taking place in Golden Gate Park that weekend.
The Hardly Strictly Bluegrass Festival: http://www.hardlystrictlybluegrass.com/
It's free and really captures the post-sixties vibe of the city. There'll be incredible music played at beautiful stages throughout the park, excellent concessions, and the warm, liberal, open, accepting spirit, which still defines San Francisco today.
I strongly suggest a trip to Hardly Strictly Bluegrass on the Friday or Saturday before the game.