How can you tell the old Mexican Peso currency from the new Mexican Peso currency?

Answer 1

Generally speaking, all coins and banknotes dated 1992 and earlier are the old peso. The effective date of the remonetization was 1 January 1993.
Here is a link to the banco de Mexico website (Yes, it's in Spanish. The Tipo AA and Tipo A banknotes are the old pesos and have been demonetized. The Tipo B notes are the first of the new pesos).
You may contact me if you have further questions.

http://www.banxico.gob.mx/billetesymonedas/didactico/billetes_FabCaractHis/billcanj/equivalencia_billetes.html

Answer 2

The old one's taste like taco