After the Alemany Farmer's Market, my SO and I love going to this little Vietnamese place in the Excelsior on Mission and Francis, right near the new Exclesior Library.
We always get the bun, and their noodles are crisp, never overcooked. Also, the egg rolls are excellent. They've got the usual complement of Vietnamese dishes, all in a convered old diner.
If you're ever way out there on Mission St (but still in SF), this place is worth a try.
I'll also recommend the Chinese place on Mission right across from the Safeway in the Excelsion. I think it is called Kong BBQ, and it fills up with contractors at lunch. I like their bbq pork with tofu lunch special - good pieces of pork in a strong sauce. I always wondered how to cook that bbq pork.
Don't forget the Excelsior!