From the Government of Canada website....
Entering Mexico
As of March 1st, 2010, all Canadian citizens need a valid passport to enter Mexico. Canadian citizens without a valid passport will not be allowed entry into Mexico and will be returned to Canada.
In order to avoid delays and misunderstandings, we strongly recommend that you travel with a passport valid for six months after your arrival date.
http://www.canadainternational.gc.ca...as.aspx?view=d