We are in the gate of Argentinian Patagonia. Carmen de Patagones is in the south of the province of Buenos Aires, and Viedma, in the north of the province of Río Negro, the most northern province of the east coast of Patagonia. The Río Negro river is the natural border between both towns and both provinces.
Because of the lack of cheap accommodation, people travelling on a budget can't stay too long. Fortunately, the towns are small enough and you don't need to stay longer.