the charges vary between card providers, some will charge you a fee for each with drawal, others make their money by offering a lower exchange rate. I found the charges for using a visa/mastercard in the ATM varied from 1.5% to 2.75 depending on the card I used - it's boring but if you have more than 1 card read the terms and conditions before you go to see which one offers the best rate. Using a cash card rather than a credit card will probably encourage you to stay within budget as you can only take out how much money you actually have, though the credit card is great for those expensive impulse purchases. Also, try and make sure you pay off your balance as soon as you get home as the credit card interest rate is extortionate for cash advances, and the interest is usually applied from the date of the withdrawal rather than your statement date.
Sorry for waffling on... Hope this helps