I just noticed this post is quite old, but I already wrote this so I'll just leave it...

"I hate pee in the punch bowl, but SF has virtually no authentic taquerias, especially not Taqueria Cancun - with the exception of their tomatillo / avocado salsa, which you find in several regions in Mexico and all over Mexico City. Why do SF taquerias fall short? They all cut corners...crappy tortillas, reheating carne asada, pastor, etc on flat top grills - which basically steams the meat, imparting little or no carmelization or charcoal notes, sloppy construction that lead to tacos that fall apart, etc.

I have to assume that the Phoenix area has a handful of places, like LA, that don't take the easy way out. A general rule of thumb I use is if they aren't making their own tortillas look elsewhere.

Best of luck seeking them out! I'm off to spring training in a few weeks and thus constructing my list of places to hit..."