My wife, my baby daughter, and I stayed at Juan's place for 6 weeks.
The hosts were very nice and accommodating, even sent a bottle of wine, as well as some electric heaters after we asked for them because of the cold weather.
The place is greatly located in a quiet corner of the trendy Condesa neighbourhood.
It is nicely furnished, and it was quite easy to make it child-safe. It's not huge, but it was big enough for the three of us. The kitchen and the bathroom are both very small. The kitchen's equipment is basic, but sufficient.
The biggest issue we had, which wasn't resolved, was a very disagreeable smell emanating from somewhere inside the kitchen. We couldn't quite locate it, but it was especially noticeable after being gone for a day with all windows closed. This actually tainted our experience significantly.
Other than that, the place was very clean.