[gd2]

My experience is that Mexicans do have many words and phrases for sexual references, with a goodly number involving foods. But I haven't experienced, or remember seeing, it using to make a joke of foreigners. That would be more like being mean to someone who can't be expected to understand than being funny among friends..

[mark212]

... which describes accurately nearly every minute of my fours years as an undergraduate (in the US).