ATMs are every where and given the scams out there it is six of one half dozen of the other if we are going to compare the advantages of using either a cash card or charging everything.
However, if you decide to use your ATM card, here are the rules:
Do not use them after banking hours outside of the bank. All of the machines down here are the ones that retain your card while you transact your business. IF the card gets stuck, as they will from time to time, it could be a week before you see that card again, and it is irreplaceable, so you cannot afford to lose it. Use the ATMs located inside or at the bank branches during bank hours. If the card is stuck, they will get it out for you. Also some of the machines down here are rigged by crooks in a scam to get you to reveal your coding, so you should never use isolated machines.
Also never use isolated machines at off hours becuase you could be mugged ( though unlikely where you will be)
You will get the standard exchange rate, and if you bring cash (not checks) you might do better exchanging money but the hassle hardly makes it worthwhile. Bring travellers checks just in case. Always good to have some back up plan.