Here's the problem. Canadians like to vacation in Mexico, but the Canadian cell phone providers do not have any reasonable data plans for roaming in Mexico. Roam Mobility is advertising Mexico service now, but it's really T-Mobile roaming and is still stupid expensive.
Option 1 is to get a SIM card from a local provider while you are in Mexico. If you speak spanish, this could work well for you. You'll need to find a cell phone provider, get a prepaid SIM card, and then go through the activation process.
Option 2 costs you about $10 more, but they ship you the SIM card ahead of time and it's already activated. I chose option 2 which is www.mexicosimcard.com. They charge $20 for the SIM card instead of the $10 that the local provider charges. In my mind it's well worth it to have a card that just plain works.
You need to have your phone unlocked to use the SIM card, but assuming that is done, all you need to do is swap out the SIM card and you're good to go. For about $100, I had 3 GB of data 3 hours of talk time back to Canada and the US.
It was nice to have connectivity when not on resort Wifi and used it to call a cab once and back home once also. Also used tethering to let the kids play Minecraft together when the resort Wifi limited the number of devices.
The SIM cards are on the Telcel network. I was in the Mayan Riviera and had excellent coverage. You should verify coverage if you are traveling to a a different area. Mexicosimcard.com suggests verifying with http://opensignal.com/. Telcel has their own coverage maps, but their documentation is in spanish.
