A Mexican grocery store clerk wouldn't make your life a living hell for being a foreigner like cashiers do in the States. Truth be told, Americans are some of the most intolerant people on the planet now that the Nazis aren't running Germany. So not being a native is okay in Mexico. The irony is the sweetest part. And you WILL find it.
Freedom abounds in Mexico.
Just because they don't have our public relations doesn't mean you can't speak your mind or own a gun. Another plus is no extradition. If you do some crimes in the United States, you can still hide out south of the border like a damn cowboy or something. Another great way to make money while in Mexico is to steal cars from tourists and sell them in chop shops. Rental cars are a nice pick if you get to feeling guilty easily.