Mabel's place is great. The location can't be beat! We had everything we needed close by including the train and bus stations, shops, restaurants and cafés, laundry services and more. Mabel and her brother Flavio were so incredibly accommodating. They were always available to answer questions and made sure to check-in with us to see if there was anything we needed. On top of that, they went above and beyond and assisted us in arranging some storage for our luggage. Fantastic service, we wish we could have stayed longer, thanks Mabel!
The only one thing I might mention is that the apartment is not very soundproof. For us it was no issue at all since we always sleep through most noise while travelling but could pose a problem for some.
Tip: Go eat across the street at the restaurant called Péron Péron, it was our best dinner of the trip! Also go down Paraguay street to Juan Bautista Justo Avenue and explore both the outdoor mall/market and the playground across the street. Have coffee and breakfast at Le Pain Quotidien.