Just got back from Argentina and had zero issues paying for hotels with pesos.

Both the PH BA and PH Mendoza said that most tourists pay with cash (as I checked out of each with my piles of pesos, other hotel guests were doing the same thing). On the other hand, the Sheraton Iguazu said that most guests pay with credit cards or are prepaid. But I did not have any issues using pesos there either.

However, budget extra time to check out if paying cash. It'll take time to count dozens (or hundreds) of bills, and if it's a large property, other guests will probably do the same thing which will make check out for everyone take longer.

Not sure how long until the government tries to stop this though.