Definitely inform your credit card issuer before you travel overseas--or even to an unaccustomed domestic location.

I had a nasty surprise a couple of years ago when I arrived in Tokyo to find my credit card refused, even though I had informed my issuer. Fortunately, my debit card worked (same credit union, so ???), but having written a bunch of checks before leaving, I didn't REALLY have the money in my account.

Once I was settled in my hotel room, I dashed off an e-mail to my credit union. Thanks to the time difference, there was a reply by the next morning, Tokyo time, in which the credit union apologized, transferred the charge to my credit card, and assured me that my credit card would now work.

Whew!

The moral of this story: Always carry a backup source of money.