But you lose on the bid/ask difference -- twice: once converting to USD, and again converting to CDN dollars.
If you have a debit card, land in Montreal, in the airport go to the nearest ATM (bank machine), and withdraw CDN dollars. The exchange rate is usually quite good. You'll be charged $3-5 for the transaction (depending on your bank and the ATM), so (1) withdraw the maximum, and (2) when you get settled, open a bank account, and wire-transfer a larger amount to your CDN account. Set this up with your bank before you leave your home country.
Cost should be about $50 (depending on the amount wire-transferred, so that represents about 10-15 ATM withdrawals.
This topic was covered thoroughly soewhere else, so search for it -- lots of good ideas were offered.