This is an amazing location, just a few minutes walk from the Prado in a beautiful neighbourhood filled with yummy, inexpensive restaurants, bars and cafes.
The room an en suite bathroom were super clean and the building was reasonably quiet (only noise comes from other guests using bathrooms as in many bnbs or budget hotels).
Cesar isn't a resident host, but was helpful. His grandparents were very pleasant although there was a bit of a language barrier as I dint speak any Spanish.
For me the only downside was the size of the room and it's impersonal feel - it's much more like staying in a small budget hotel than an airbnb, which for some people might even be a plus, depending on what you like. I had a medium size luggage with me and realistically the room was too small to accommodate it easily - if it was open then I could either open the shower room door or the closet but not both, and I couldn't open the room door. However for someone travelling with just hand luggage it would be fine.
At the end of the day it's a good, cheap room in a great location.