SIM card for cell phone question.

Make sure that your phone is "unlocked". IE it will work with any provider as long as you have a sim card.

We have been doing this for years. We have sim cards for Canada, USA (AT&T) and Mexico (Telcel). When we travel to Europe we get a sim for the first country. (Note for Europe you will need a quad band phone.) I THINK but cannot guarantee, that phones in Canada, USA and Mexico are on the same frequency band.

If you return to Mexico at regular intervals you may be able to reuse the same sim and maintain the same number. It depends on how long the time on card has expired. You should be good for 6 months or so after expiry.