For an upcoming trip, I'm going to spend about 10-15 days in the USA, followed by about another 10 days up in Canada. While over there, I expect I'll want to make and receive a few phone calls, send some texts, and probably use a few tens of mb of data too. Looking at the roaming prices for my UK mobile in the US and Canada, this isn't something I'm going to want to use my normal phone for...
In the past when I've only been in one of the USA or Canada on a trip, I've picked up a Pre-Pay GSM sim card, and it's all been fine. For this trip, I'd ideally just get the 1 sim card to cover the three weeks. However, I'm aware that it's quite rare for pre-pay sim cards to work outside of their own country. (European ones tend to be the exception I've found, no other ones I've got ever have done)
So, I'm wondering, do pre-pay sim cards bought in the states normally work over in Canada, and if so, are the prices when roaming there normally sensible or insanely high?