I stayed at Cecilia's place for a month and a half and wish I could have stayed longer. I've stayed at several Airbnb's and this was definitely by the far the best -- great location, huge bedroom with comfortable queen bed and a large desk (with solid internet, 20+megas) for working. Where her apartment is, there's very little street noise and I slept well every night (mind you, I normally wear ear plugs but during the nights I didn't, I was fine). Oh, and I had a private bedroom. The living room is enormous and has nice views of the city, especially at night. As far as the neighborhood, it is right in the heart of Condesa which for me was exactly what I wanted. You are only a few blocks from the metro and have access to some great restaurants and markets around Condesa. Plaza Espana is only a five minute walk and Plaza Mexico only 10 minutes. Bosque Chapultepec is also only a five minute walk from the apt. as well. And the entire area feels very safe, even late at night.
Lastly, Cecilia and her roommate (who is usually traveling) are super nice and fun to chat with. Cecilia will go out of her way to make sure you're comfortable and have everything you need for great visit. As an example, I asked about improving the Wifi and within a day there was a new router installed and a strong connection from my bedroom. In short, can't recommend this place enough, whether you're staying short-term or long-term, you'd be lucky to book this place if it's available.