There are tons of great restaurants in San Francisco.
The first place I would go to is the upscale, farm to table, vegetarian restaurant The Greens
This place sounds very interesting, it’s vegan food meets inventive fish dishes at Dante’s Weird Fish in The Mission district.
If you like ice cream and you have an adventurous palate, check out Humphrey Slocombe
For Mexican tortas and breakfast, at reasonable prices, you might like La Torta Gorda
This place sounds like fun, Foreign Cinema dinner and a movie.
If you’re into photography, This Site gives you some ideas about the best places in San Francisco to take photos.
Walk across the Golden Gate Bridge. It’s truly amazing. You’re up there so high in the air and it’s very windy, and the views are spectacular. Great photo ops.
And like some of the others have said, do not miss visiting Muir Woods
There’s lots of Public Art to be seen.
Take a free, self-guided tour of Chinatown
Put on your love beads and Burkenstocks, put some Doors music in your ipod and head to Haight Ashbury
Visit Coit Tower
Go for Coffee
Sample some Sourdough Bread
Take a ride on a Cable Car
Have afternoon tea at the Fairmont Hotel
Go to a Show
Have a great time!