I live in Iowa. Lots of Mexican restaurants where native Mexican's serve good food. However if you have actually been to mexico you will know it is only vaguely related to Mexican food as served in Mexico. If you speak Spanish to the help they will admit they don't eat the food where they work because it isn't like home.
On a long road trip across the southwestern USA when I was a child, we went into a Mexican restaurant in Yuma, Arizona, where no-one spoke any English.
Fortunately, the owner's teenage daughter came home for lunch, and she spoke English, but she didn't know translations for what was on the menu. My mum asked her what she was having for lunch, and then asked for the same. The girl translated for her father, he grinned, and brought the best meal of the trip.
I've heard the same comment from Mexican immigrants, but for different reasons. A Mexico City expat friend of mine derides all Mexican restaurants, even the higher-class ones are just "ok".
I suspect that Mexican dishes highly according to the part of Mexico, but experience in higher quality Mexican restaurants in DC leads me to believe there is also a huge quality difference.
There are definite regional differences according to my wife She grew up just a couple miles from Mexico so a vacation in Mexico wasn't a long trip, plus the random Sunday "lets go to the other side of the river for lunch and cheap sugar" trips that are possible when the country is that close. I have never lived close enough to Mexico as to make it the trip a non-event and so I don't have personal experience to report)
Ah, I'm curious because it's not uncommon to see some restaurants and bars patronized by food service folks. SFGate periodically runs "where do the chefs eat" type human interest stories from time to time.
Funny thing about Lolinda, one of their line cooks stabbed some guy to death. I was on the jury and man did that case reaffirm my cynicism towards our judicial system.
There are a handful of less casual Mexican places in the Bay Area, but not many (Tres Agaves and Nopalito come to mind). Lolinda is actually Argentinian, not Mexican, though.
I've lived in Las Vegas, The Bay Area, and Salt Lake City and Mexican Food definitely gets the appreciation it deserves here.
My favorite restraunt Utah doesn't even serve Mexican food... they serve "Imperial Aztec Cuisine from Mexico City"