I stayed at Benjamin's place for a month and I enjoyed it.
The place is very clean and very well equipped. The room is not super big but there is a big closet, a really comfy bed and a little desk in case you need a home office. The internet is great. I had no problems working there.
The street where the flat is located is safe but the area Tacubaya may seem a bit scary though it is nicely located. It'll take you about 20 minutes to walk to Condesa and 30 minutes to get to Chapultepec.
The metro station is a 5 minute walk.
There are 2 markets nearby.
Benjamin is really friendly. I didn't see him much though.
Thank you, Benjamin and Fabian!