In some touristic destinations, such as Cancun or Los Cabos, you will (often) be able to pay in US Dollars. But keep in mind that Mexico's official currency is the Mexican Peso, not the US Dollar! This means that you shouldn´t always assume that you can pay in US Dollars. Outside touristic areas, it´s very unlikely that US Dollars are accepted. So, be prepared and withdraw Mexican Pesos once you arrive.