I use a travel Debit/ATM account with Bank of America. They have an association with ScotiaBank (their ATM's are present on the Dutch side) with no ATM fee. You can use dollars everywhere so no need to worry about currency exchange fees. I keep a nominal amount in the travel account in case my debit card gets compromised, then add funds via online transactions as I withdraw. Avoids packing down so much cash or having a lot on me or in the safe. I was a bit surprised after our fall 2013 visit as I found that my credit card when used at Dutch side grocers did charge a currency exchange fee, dollars to guilders. I now have one that does not. Also keep in mind that you probably will have to pay in cash for gas fill-ups if you have a rental car.
Have a great trip, you will love the island, diversity, and all the great beaches and great food.