Good for you! However, I have been to Mexico twice in my life as a tourist, and neither time was I either required to get immunization, or did I opt to get it. The only bug we came back with was ...my then husband 'caught' a case of Montezuma's revenge in Nuevo Laredo. That was probably from drinking the water (or ice cubes?).
My point is, most people don't bother with immunizations before touring in Mexico. And those legal citizens that go back and forth visiting their relatives there don't either. So...maybe immunizations should be required of anyone crossing the border from now on.
I suspect that Cancun and Cozumel, which is where most people go touring in Mexico, is probably a lot better regulated and cleaner than the rural areas and the vast slums of Mexico City.