[getbak]

It depends on where you're going, and who you bank with in Canada.

I've never had trouble using Traveler's Cheques in tourist heavy places like Vegas, L.A., or Orlando, but you might have more of a problem in smaller places, or places that don't attract as many tourists.

Using local ATMs can get expensive because you'll probably have to pay something like $5 per transaction to your Canadian bank, plus whatever fees the machine itself charges.

TD and RBC both have some US branches and if you're a Canadian customer with them, you can withdraw from their branded branches in the States the same as you can in Canada, with no additional fees (other than the exchange rate, of course). There are quite a few TD branches in Boston, for example.

Buying cash locally before you go will get you the best exchange rate, with minimal (if any) fees, but you run the risk of losing all your money. Traveler's cheques give you some security, but are a little more of a hassle to use. ATMs are convenient, but the fees will add up quickly.