I'd suggest using a credit card when you can but bring some Canadian cash taken out from your local bank for snacks. If you need to take out cash when in Canada, I'd probably take it out from an ATM from a major bank (Royal Bank (RBC), Bank of Montreal (BMO), Toronto Dominion (TD), CIBC, Scotia, Van City). Obviously don't withdraw from a no-name/private ATM which are sprouting up everywhere. I don't know what the exchange rates they give at hotels but in supermarkets, McDonalds, etc, it's brutal. Travellers checks aren't worth the hassel for most situations IMO.