Replying to Herro NS please school me on San Francisco

Ill have 6-7ish hours on the ground there next friday. Ive already figured out how to take the train from the airport to downtown and back.

After that whatcha got? Ive never been, but i take the mentality of to travel is better than to arrive, and off the beaten path is better. (AKA im not spending the money on Alcatraz)

Also whats good to eat thats cheap, does SFO have its own Gyro type food carts like NYC does? something along those lines for eating.

Thanks guys!