VZW TravelPass to Canada lets you use your existing plan limits and costs $2/day (or 24 hour period, actually) in CA and MX. You have to explicitly turn it on in your account, but my wife used it for a week long trip (not every day) and it cost us $8. Mine is covered by work. For a 14 day trip, it should cost <$30, which is fairly reasonably.

If you have TMO, then there is no extra charge to use your phone internationally.

The AT&T Mobile Passport and Sprint International Data Pack plans are terrible (low data limits and expensive) and I'd just get a local SIM.

Older thread, but might give you some ideas.
http://www.flyertalk.com/forum/trave...im-canada.html