I can highly recommend to stay at Irinas house. Irina and her mother are very helpful and make you feel at home. Everything is very well organised and there is a lot of space for many travellers. More of the people are staying for a longer period of time and this makes the place even more calm and relaxed. There is always someone to ask for advise, or simple to have a nice talk with.
It is near to public transportation and the area seems quite safe.
I will definately come back to this Airbnb If I ever visit Buenos Aires again.