Yes, there is normally no problem using either bankcards or credit cards that allow cash advances at the ATMs (cajeros) in the area. They actually pay the best exchange rate. There is an ATM located in Barra between the Jardin and the Police Station and there are two more in Melaque at Banamex across from the bus station. There is also an ATM in both Banamex and Bancomer 18 km south in Cihuatlan.