As for saunas, when I was in Buenos Aires a few years ago I enjoyed A Full sauna. It's clean, modern and there were lots of good looking guys. Some private rooms have glass ceilings where people on the upper floor can see what is going on below.
I don't remember there were many saunas when I was there. But currently there are at least 6 saunas.
I stayed at the 4* Bisonte Palace hotel, but I would say it is similar to the 2*-3* Pinnacle hotel in Bangkok!. It is conveniently located right in the town centre in the middle of shops and restaurants with a Metro station a few steps a way. I found it quite handy when I got to downtown from the airport by the Airport Express bus, as the bus station is just 3-minutes walk to the hotel. It is also about 15 minutes walk to A Full sauna. It served very good breakfast which was and is included in room rates. I remember I paid just about US$22 for a double room with breakfast for 2, but it now costs $65 at expedia.
Bisonte hotel website :
http://www.hotelesbisonte.com/English/index_en.htm