I have spent a lot of time all around Mexico. This is the real deal -- it's like eating in a hole…read morein the wall taqueria in Guadalajara.
This place is for people who like authentic Mexican low brow food, rather than Tex-Mex or "Gringo" versions of the cuisine. It is also for people who, when they walk in and realize that they are the only non-Mexicans in the joint, view this as a positive sign that "this must be the place" rather than one which engenders self consciousness. I can almost guarantee you will be the only native English speaker in the place (unless I'm there...)
As for ambience - there isn't any, which is to say that it's perfect. It's flourescent lights, formica tables and steel chairs with red vinyl. Mexican tv blaring cheesy soap operas or soccer above the counter. Phone cards to call back to Mexico for sale. Just like Guadalara.
Now let's talk food. If they don't bring them to you, ask them for some grilled jalapenos. They are fantastic, but be careful. The chips are prepared fresh and the hot sauces in the squeeze containers on the table are home made.
The tacos are all-world. "Al Pastor" (spiced pork), "Carne Asada" (grilled steak) and "Camaron" (shrimp) are the best, and come piled high with the filling, cilantro, onion and a lime wedge. At a buck fifty each, they cannot be beat.
The tortas are Mexican hot sandwiches. Order the "Carne Desebrada" - pulled beef. It is a meal in itself, with avocado, jalapeno and the most addictively flavored beef you will ever eat. I have friends that swear they are made of heroin.
Other standouts include Shrimp Diablo (spicy shrimp), Chile Verde (pork in heavily spiced tomatillo sauce), Burrito al pastor (a burrito with the same filling as the tacos mentioned above), and fajita mixta (fajita with the kitchen sink). There are also lots of other "deeper" Mexican dishes like shrimp cocktail in tomato juice, menudo, various "caldos" and mojarro (a whole fried fish that you pick apart with your fingers).
Drinks are Mexican beer, sodas, water, horchata or, if they have it that day, "agua de melon", which is cantaloupe juice that is out of this world.
The place is CASH ONLY. Manuel and Ana, the owners, speak decent English. No one else does at all. They will always be there.
Finally, back to the ambience/clientelle . I am not going to get into a whole social commentary thing, but if you are the type of person who will get jumpy walking into a dive where the people eating are guys who work landscaping, construction, etc. this is not for you, as this is precisely that place. (I literally hired a guy to do some drywall work for me while having lunch there one day.) But to put your mind at ease, I routinely bring my kids, wife, friends there and we are welcomed like family. No one is going to bite you. You, however, are going to want to bite their food.