Don't use a Canadian credit card at all in the U.S. Use a U.S credit card like Visa or MasterCard issued from a Canadian bank and have a U.S. account set up in your Canadian band. The card will automatically pay you statement every month if you wish from your US account so there's no extra 2-2.5% surcharge.
If you are going to the same place each year, then maybe it pays to open a local US account in an American bank.
The currency news has not been encouraging in the last few days. Some economists are saying the exchange could go to .70 by spring 2016 which is 42.8%. There was one projection saying in the next 5 years the exchange could hit a low of .55 or 81%!
Who knows.
Toban