Looks like the closest location for xoom would be in Comodoro Rivadavia, Chubut. No experience with it though. The only time I got pesos in Bariloche was from a arbolito operating out of a souvenir/t-shirt store near the centro civico.
I used to drive across the border to Osorno in Chile and get Chile pesos out of the ATM; change them to US$ in the casa de cambio there, then drive back again!