okay, it appears that you guys have failed to recognize the obvious.
What these pizza parlors are doing is catering to the illegals who are crossing the border.
No one who works or even collects welfare in America for a day is paid in pesos.
Didn't miss anything... some are illegals...some are Mexican tourists visiting US relatives on tourist visas, some are Mexican Americans coming back from Mexico. I've come back from Quintana Roo with 20 Bucks worth of pesos or so and I'm a Gringo.
Uh, no, you are making assumptions.
Where I live, many hispanics have pesos, they cross into mexico and back every few weeks.
If you live near the border, you may accumulate pesos pretty easily. In fact, I got 10 Nuevos Pesos sitting on my desk in change left over from last week, and lots more laying around in jars from previous trips.