i googled "why mexicans don't like gringos" and the first result is very informative:
http://www.fredoneverything.net/MexicansDontLikeGringos.shtml
it's really hard of a concept to try to explain, but when you know that your country is full of shit, and that by being a burger flipper on yours nets you really really really good money, then people get resentfull
Just as an example: i'm a computer science engineer, and i'm in a well paid position, supposedly, and i make 3.70 dollars an hour. Hey, guess what, that's like half the minimum wage on your country. yup.
and because almost everything comes from china or the us, we gotta adjust to those price, but, you must also add the customs and extra taxes: arond 70% more ...
in perspective, xbox games come out at around 1300 pesos (around 110 bucks) and things like the xbox360 4gb is around 4500 (400 bucks).
so, we have to work double, to get the same things as you guys, for like 2 times the price. And that is just the tip of the iceberg ...
imagine if you will, that you tell someone that you will employ them for 5 bucks an hour. No school, no capacitation, no nothing, just work, and 5 bucks per hour.
Now, think of some dumbass who spent 24 years of his/her life on school, to earn less than some "mojado" that didn't study, and even has time and money to drink some "cervezas" at the end of the day, while another bunch can't ...
you see, in mexico, being ignorant gives you value, because if you aren't, then you might become a problem, and you can't even find a job. You're overcapacitated, and that means that you have to earn better money. But why pay if someone can do the same thing as you for a fraction of the money!?
i'm not exactly how to express it, but part of the problem is also the easy money, and what people are willing to do to get it.
'anyways, this thing i just typed is full of spelling errors, and i won't bother fixing them.