Is this a gourmet mexican restaurant? No. Is it some of the best mexican food I've ever eaten? No. Is it a good, cheap place to go eat lunch? Yes.
My office is located about 2 miles from El Vallarta. My co-workers and I take a trip for lunch once or twice a month. The service is ok. They give you chips and salsa, as well as a queso and bean dip. Although the food isn't anything to write home about, it is fairly cheap. They have great lunch time specials. I usually get the fajitas, which is $5.95 (I think)...and they are actually pretty good.
So, like another reviewer posted, I probably wouldn't recommend someone to make a trip to Concord simply to dine here, but I would suggest it for a lunch-time visit if you are in the area.