Yes—the US dollar is Ecuador's official currency. Since 2000, Ecuador has been fully dollarized, meaning you don't need to exchange money, calculate rates, or carry local cash. Your US dollars work everywhere, exactly as they do at home.
In the late 1990s, Ecuador suffered a catastrophic financial crisis: the sucre collapsed, banks failed, inflation topped 90%, and poverty surged. In January 2000, President Jamil Mahuad announced dollarization to stabilize the economy. It worked—inflation dropped to single digits within years, and the banking system recovered.
Ecuador uses US coins (pennies, nickels, dimes, quarters) plus its own centavo coins (1, 5, 10, 25, 50 centavos = same values as US cents). Both systems interchange freely. You'll get a mix in change.
Ecuador has no control over its monetary policy—it imports US Federal Reserve decisions. This constrains domestic economic management but provides the stability that dollarization was adopted to achieve.
Bottom line: pack US cash (small bills), a debit card, and a credit card. You're set.