If anyone is going to Canada, the story your US bank tells you about using their credit or debit cards is not the same as reality. I had trouble in 2007, 2008, and trouble again on my 2009 trips.
First of all, some major brand gas stations refuse to take US issued cards at all. Even if they do, you may find that some cards work and some cards don't work. You may also find that your bank has shut you off because they think your card is stolen, even if you haven't reported it and even if you told them ahead of time that you would be traveling outside the US.
Recommendation: carry two cards and preferably more. I carry three and had one instance where none of them worked.
Most places I've travelled in New Brunswick, Quebec, and Nova Scotia take US cash, but there are exceptions. It's best to travel with both US and Canadian currency.
Finally, when you use a credit card, a hold is put on your funds when the merchant swipes the card. The amount of this hold is entirely up to the merchant. Most are reasonable, but many are not. The following is an example. All of these are gas purchases, which should resolve to about $17 each.
As I type this, it's September 7 and the "pending" transactions have not yet been released, meaning I can't access hundreds of dollars of my money.
If you're staying in hotels, it can get much much worse. I've had situations where I bought a $125 hotel room, the hotel put a $300 hold on my funds, I paid cash in the morning, and the $300 hold was not released for 10 days. This could be a huge problem with $425 tied up for each day of travel. I thought I had $2,000 of headroom in 2007. Not so. I hit the limit with false "pending" charges. I was glad I had enough cash to get home.
I've talked to my banks about this and they categorically deny it happens like this, but this is reality folks.
Be prepared. Pay cash if you can. Get Canadian cash before you leave the US and carry multiple credit cards with high limits, just in case.