ATM is the only way to go.
Several years ago (30) we had a ATM installed in the lobby of the Museum where I worked. I was watching it on it's first day and observed a woman get some cash from the machine and was looking very perplexed. I went over and asked if there was a problem. She held up a fist full of dollars and said "It gave me Canadian money" I replied "well yes this is Canada". She looked at me and very adamantly said "but I used my American Express card"
So you can get Canadian money even if you use American Express.