Letting your credit card companies know you will be travelling abroad is a good idea - additionally, most US credit card companies have a toll free number you can call them while travelling or will accept your collect calls - you can check this out at their web-sites.
While you are checking, look into the 2% or 3% charge - in most cases these charges only apply to charges in foreign currency - if you are billed in dollars while travelling the fee usually does not apply.
Have a great trip.