It would be nice to know what a typical Mexican tips. Do they tip at all, 5%, 7%? we should base tipping on what they usually receive. We should not export the insane method and percentages of tipping we use here in the states. I personally think that tipping should never be based on the price of the meal, but an amount of your choosing based on what level of service you received. Pick a set amount per person being served.
A waitress serving breakfast works just as hard as a person serving dinner, but typically the price of the dinner is much much higher.