Probably the best thing about using credit cards when traveling overseas is that credit card purchases are exchanged at the interbank exchange rate. That's usually the best rate you can get for currency exchange. However, you may be charged a currency conversion fee by that issuer each time you make a purchase. In most cases these fees are lower than if you exchanged money at bank or facility in that country.
Check around and find a credit card that doesn't add those fees. You can find a list at www.cardhub.com.