JWKessler, check with your provider for roaming in Canada. From what little I know iPads sold in US are locked to the provider and come with micro-sim already instaled. iPads sold in Canada are not locked and the provider / micro sim is installed by the owner. Through a bunch of rigmunro there is a way a Canadian can get AT&T micro sim from a US Walmart and use the iPad in US. There are alot of posts made arround the beinging of this year about this topic, hopfully you can find them, they may help you.
You could stoop to using free WiFi, there is a free App. called Free Wi-Fi Finder that will help.
PS I should have read through the sticky "Travelling With iPad" your answer is there.