This guy gets it, it's incredibly easy to find good Mexican food. Why eat something that legally cannot be called meat?
Best Mexican food that's open at 3 is probably Filiburto's, but living in Arizona certainly has spoiled me on eating crappy Mexican food.
The best Mexican food I have had at 3 am is Taco Bus down in Tampa, it's open 24/7 and is the only real reason I go down to Tampa. Cold pizza the next morning is probably one of the greatest breakfasts ever and I start every morning with a cup of espresso. So yes I have.