The best way to get pesos when visiting Isla Mujeres is to withdraw cash from ATMs located near the ferry terminal or in banks and grocery stores around town. Most ATMs accept American Express, Visa, Mastercard and debit cards.While many restaurants, hotels and shops accept US dollars, it will usually be at a lower exchange rate. There is also a money exchange inside the ferry terminal and across the street. Foreign coins are not accepted anywhere and should never be used for tips.