Back when I was with AT&T I obtained a plan with 1700 minutes per month, unlimited roaming in Canada AND Mexico for $99.00 per month. I migrated the plan over to Cingular, but when I told friends about it, they were told that the plan is no longer available. The plan does require at least 50% of the minutes each month to originate in the US, which is no problem for me, but it still is a great deal. It is a North America plan, so calls from MX to CA are also included as well as vice versa.

Now once I get to Central America, they get their pound of flesh back, but I have other means of dealing with that problem.