Depends what you want to do with it. Do you want to use roaming or you want to get a line in Mexico using your cell phone? Who provides your cell phone service? Make sure that your GSM device is compatible with the GSM network frequency of the country. For Rogers you can go to:
I was on hold with Bell Mobility when i wrote that. They said my phone won't work unless they do something to give me access in mexico. so now it's done.