"Oh one other thing that was an annoyance I thought I did get. That was the "Gringo, wait - Mexicans first." Seemed like several times in several places people thought nothing of butting in front of me and the counter help were only too happy to look right through me to help the "other" person."
I can't say I have ever run into this problem (in nearly 20 years "in-country".) If I had, I probably would have said something to the effect, "Hija, hay fila!" Of course, if the person butting into the line was a cholo with a bunch of prison tats, a shaved head, and with a squarish bulge in the back of his shirt, I would probably just keep my big mouth shut.