Credit cards make things easy, for sure, but if your bank charges international transaction fees (as did my credit union) they can add up after a bit. Personally, I used my card for things like gas and hotels and cash for smaller purchases (like donuts and coffee at Tim Horton's). So near the border, most businesses take US dollars as payment, but the rate won't be to your advantage.
One last bit of advice: if you use a Smart Phone, or a tablet with a data service, make sure your service provider includes Canada. If it does not? Turn off "roaming data" in your settings, or put the device into "airplane mode". Otherwise, you may get a rude surprise on your next statement (even if you don't make or receive any calls or text messages).
Most hotels and restaurants offer free wi-fi, so that's what you use instead.