Your US drivers license, in good standing, is honored by Mexican law if you have Mexican approved or sold liability insurance.
If you don't have a US license, you don't have a Mexican license.
I dont give a crap about what is legal or illegal.
WILL THEY ASK TO SEE A DRIVERS LICENSE WHEN CROSSING INTO MEXICO BY CAR?
WILL THEY ASK TO SEE A DRIVERS LICENSE WHEN RETURNING FROM MEXICO BY CAR?