I've just exchanged a few udst/ars just for the sake of trying. They accept only USDT (Tron) 1.5%. They also accept USDT (ERC20) but at a higher rate.
I really don't know because I am not from Buenos Aires but few minutes ago I found this in Palermo.
https://maps.app.goo.gl/B7i4r4sQTNJ66xDp6
It is not a recommendation, I have never used the service. 
Discussion
Cool, thanks for info. Fascinating how Tron ended up being rails for actual money transfer, lol. Decentralization theatre is unreasonably effective!