The best way to use money in PDC is by your credit card as you will get a better exchange rate. Make sure your card does not charge a fee for international transactions.
Some places only take cash so it is advisable to have some cash on hands. You can get better exchange if you use your ATM card.
AVOID the ATM machines that are located on 5th Avenue. They charge very high fees. You can do better by walking to 1oth Avenue, which is where most banks are located. The fees are lower at bank ATMs.