I guess it's not comparing apples to apples but if you've ever known anybody that participated in a student exchange program in Mexico, it's safe to say that they aren't exactly more welcoming. Is two people considered a small sample size?
I was talking about just taking a vacation to the USA, so not apples to apples for sure. It's easy as heck to visit for up to 180 days.
With that said I am guessing that a lot of the people in Cancun hate Americans even if they act really nice while at work with us.