i only went to 2 restaurants while in san francisco, actually went to both of them twice. california pizza kitchen, which you will find on geary st, between taylor and mason i believe. and the other was lori's diner located on powell, about a block from the cable cars and muni station.
Favorite Dish: california pizza kitchen. i got the tostada. it is pizza crust with black beans, cheese and lettuce, tomatoe's and ranch dressing. i had it w/out the dressing though. very good. cost is around $9.00 for about a 10 or 12 inch pizza. i also heard someone mention that the tiramisu was wonderful, although i did not try that myself.
lori's diner- i had grilled cheese and french fries. cost is around $6.00. this diner has a nice 50's atmosphere with neon lights, old signs, and old fashioned waiter/waitress outfits. has a nice kitschy feel.
if you're tight on money when visiting san francisco, go to a nearby walgreen's or other marketplace to pick up your food. san francisco is well known for it's fine and varied dining, but not known for being inexpensive.