Also try Garajito and (the somewhat unceremoniously named) G-Spot across from Moscone on 3rd.

And if you're a fan of poor life choices or post lunch naps, then their Zapatos are excellent!

These recommendations would have been great 6 months ago; unfortunately I just moved to San Antonio.. Actually, I'm flush for great tacos now :D

Amazing burgers also :) Love that place.