We've been to almost all the taquerias, most of the full service sit-down restaurants, and three taco trucks in the tri-valley area. El Charro Taqueria is one of our four favorites.
The only thing that puts El Charro into the (self-described) taqueria category is that you order at the counter. They differentiate themselves from the competition by having great food, good service, and reasonable prices. I'm not sure I can think of another Mexican place in the area that has all three. A few places have two of them, most have one, and some have zero.
The menu is more extensive than most taquerias and is what you would expect at typical full service restaurants. Nine meat choices for tacos ($2) and burritos ($4/$5), four soups ($7-$11) on a regular basis, plus menudo and posole (sm $6, lg $7) on weekends, a seafood section ($10-$11), and even a breakfast section ($7) are on the menu. They have a salsa bar, which is a must for me. The chips are fresh, thin, and made from corn tortillas. I don't understand why some places have those stale, thick, flour tortilla chips, unless it's to discourage consumption. Even Chevy's and Baja Fresh have decent chips and salsa. (It's their best thing.) The chile rellenos are the best around. Many places don't bother to peel (char/steam) the chiles any more and you end up having to use a knife and fork to cut the tough skin.
The service is good and is friendly, which is a change from many taquerias where service is almost non-existent. There is outside seating. Now that Livermore has banned trucks from First Street and redeveloped downtown (apparently trying to emulate Pleasanton's downtown I guess), it's surprisingly pleasant out there.
El Charro Taqueria
2020 First Street