Patagonia's currency in Chile is the Chilean Peso ($ or CLP) and the Argentinean Peso (ARG$) in Argentina.
It's always helpful to carry a combination of local currency as well as USD cash.
CREDIT CARDS & ATMS
Visa and Mastercard are the most widely accepted credit cards in Patagonia, though many other places also accept Diners Club and American Express. You can find ATMs throughout the cities.
While traveling in remote areas, however, such as Torres del Paine, or it's best to rely heavily on cash. Similarly, camp grounds and small businesses--especially those in remote areas--are less likely to accept credit cards.
It is customary to tip around 10-15% at restaurants.