Most of the "Bankomatikos" that you will see all around the island (identifiable by their blue and yellow kiosks) are operated by MCB, Maduro and Curiel's Bank. There is a machine conveniently located in the luggage pickup area in the airport, and they are typically near grocery stores and gas stations. Regardless of location, the cost is the same flat rate of US$5 per transaction plus whatever your home bank charges for an out-of-network transaction. So better to get a large amount at one transaction vs. a bunch of small withdrawals. The exchange rate is fixed at $US 1 = Nafl 1.75. ..easier to think of as $20 = Nafl 35. The machines will ask for your choice of US Dollars or NA Guilders to be dispensed. Also be aware that if you pay with US$ most places will return your change in Guilders at the 1.75 rate, a bit confusing. To avoid all this exchange rate stuff, I use my widely accepted AAdvantage MasterCard with no foreign transaction fees wherever possible, and also accumulate miles towards another trip at the same time.
Enjoy your visit to Curaçao! Weather has been delightful the past few weeks.