Ruben's place is located exactly where you want to be. It's practically in Zona Roza, right next to plenty of great restaurants and bars, as well within walking distance to the Bosque de Chapultepec. The neighborhood is quiet safe and filled with many street-food stands majority of the day. We were late to check in due to flight delay, but fortunately Ruben's friend was kind enough to wait for us at the apartment to give us the keys.
In order to get to the apartment one needs go through three locked doors (4 different keys) which first couple of time might be a little hectic.
The apartment itself was quiet nice and spacious. There were a couple of hick-ups in regards to some of the apartments amenities, but Ruben helped to resolve them pretty quickly. The last couple of days we started smelling something weird within the apartment which we could only attribute to the smells from the bathroom pipes.

Overall, I would definitely recommend staying here.