Mexico isn't listed in many sites (e.g. this) that requires passport with minimum 6 month validity. However many others mention it along with travel.state.gov. Is there an official recommendation from the Mexican government? After all, airlines would have to enforce it as per the destination requirement so they must be getting this information from somewhere. Does someone have personal experience?
The airlines as per Timatic, which is used by airlines, states that the passport will need to be valid at the time of arrival.
Similar statement is on the page of the consulate of Mexico in Seattle:
The maximum length of stay allowed under the tourist visa is 180 days, which is likely where the 6 months validity requirement on the State Department's site comes from. It's better to a valid passport at the time of return.