If you have a Capital One ATM card you can get Euros at the Margot Post Office with no fees at the rate traded that day.
Watch out if your bank card charges foreign transaction & Currency exchange fees besides normal ATM fees. With the dollar moving up I don't see any advantage to converting to Euros. Most places post what they will trade dollars to Euros for so most times it is to your advantage. A few years ago we opened a Capital One checking account just to use for traveling in Europe & St Martin works great