As Julia says above, I wrote a review after I came back from Canada last June. The weather in the Rockies was cool (until a fortnight before we got there some of the roads were still blocked with snow) and most of the time I wore a fleece. Once we got out of the Rockies the temperature went up 2 or 3 degrees, the fleeces didn't come out of our bags and bare arms were the order of the day (until we reached Vancouver, where it was generally grey and poured with rain on our last day). So you need to adopt the layered look to cope with all eventualities.
I took some Canadian dollars and a Post Office Canadian Dollars travel card which I used both in ATMs and in the same way as a credit card. I had no problems and cashed in the remaining dollars through the Post Office on my return.
If you do go on this trip, I am sure you will enjoy it and come back with lots of happy memories. Do remember to take a good camera - I came back with over 300 on my new digital camera and still look at them on the computer.
Ann