Mexican government policy has recently changed on the issuing of tourist visas to those coming in from the US, Canada, the UK, and many other countries. All tourists are given the full 180-day visa automatically. Previously, 90 days was most common, though it was up to the immigration agent you first meet to decide.
This means travelers save the 21 dollar renewal fee when staying more than 90 days, and no more headaches at the airport or immigration office for renewals.
Tags: General Mexico Info, TEFL in Mexico