The closer to the boarder you get, the better the food. It isn't because people close to the boarder are better at making it; it is the fact taht the ingredients for true Mexican food need to be very fresh. That is a big part of the culinary process for making Mexican food, and why it sucks or tastes bland in Oregon or Canada. However it is getting better.
Next time your in Mexico, check out the produce and try it. It might not look as pretty as it does in America, but it is a tastes so much better. Warm water is also good for the Shrimp and Fish.