The apartment is beautiful, very spacious and has a lot of light, you can see all of the square with Constiución Station from the balcony and you have your own private bathroom. Juan was a great host, he was being very helpful when I lost my phone and gave me advice on cultural activities - he has a great music taste too. The neighborhood is surely not very picturesque but as busses are leaving right in front of the door and the metro station is a 3 minutes walk across the square it´s easy to move to other quarters. Literally everyone I told I was living in Constitución neighborhood (taxi drivers, people I asked for the way, etc.) told me that this was a rather dangerous place for me to stay and that I should be careful. I can't judge if that is exaggerated or not, at least on the day I felt safe, there are always people on the square, Juan himself goes to play with his little boy to play on the square.
Fun fact: Juan likes to be mocked about being a super host ;)