They will need it to work in Mexico, USA and in remote areas in Canada. Can you recommend the best product for this.

1. Rogers PAYG. This is the most expensive option by far because Rogers will rape you when you call from the US or Mexico. You will need to confirm with Rogers that the phone you intend to use will work in all 3 countries and that Rogers has set up the account to allow roaming in those countries.

2. Separate SIM (and PAYG plans) in each country. Use SpeakOut in Canada. Use a T-Mobile (or SO US, etc.) SIM in the US. Use a Mexican SIM when in Mexico. This is more complicated because you'll have 3 PAYG plans, 3 SIMs, 3 phone numbers, etc. but is by far the cheapest.

As long as the phone you use is an unlocked GSM that covers the 850/1900 MHz bands it should work in all 3 countries and will all 3 SIMs. The phones sold by SO Canada all meet this requirement.

N.B. When you say "remote areas in Canada" keep in mind that cell coverage is only available in populated parts of Canada. Generally that means the south and along populated corridors along major highways. If you plan on going into really remote areas, e.g. in the north, then no cell phone will work. You will need a satellite phone like Iridium. Expect to pay a small fortune for both the phone and airtime.