I cannot say for anything certain about ATM's at the Iberostar Bavaro. There are ATM's at the bank's near the Friusa crossroads 4 km from the resort and at Plaza Bavaro. You can change currencies in the banks or at Vimenca (Western Union) at Plaza Bavaro. The Vimenca has been providing the best rates recently. Don't worry too much about having to convert currencies just when you arrive, dollars are accepted most everywhere. When you do convert, just do enough for a day or two spending, that way you will not be stuck with too many Pesos when you leave.
Tips: Photocopy your passport, keep a good photocopy in your wallet or purse and put the passport in a secure place. The banks are now asking for I.D. when converting currencies, use the photocopy as your I.D.
You will get a receipt when you exchange currencies. Save the receipt and use it in the same bank or exchange to convert your Pesos back to Dollars prior to leaving the country. The banks want to keep the Dollars and will not convert unless you have the receipt.
Regards, PJT