According to
www.gsm.org there is GSM coverage in Mexico, here is a coverage map:
http://www.gsmworld.com/cgi/imap_gsminfo.p...rm&frame=middle I literally use my GSM 270 all over the world. If you are not worried about people calling you on your U.S. number then the economical way to do this is to purchase a prepaid SIM card when you arrive at your destination. That way you have a local number and calls are at local rates.