For a chain taco my vote goes to Jimboy's even though it's nowhere near an authentic Mexican street taco. In my younger days these were good hangover tacos...

Fortunately we have a lot of mom-and-pop taquerias around Sacramento. And many Mexican tienditas and carnicerias often sell tacos on the side. There's one near our house that usually has a portable taco stand set up, just like in Mexico. Just had some tacos de lengua there the other day. Good stuff.