Juan's place is ideally located in the Malasaña neighborhood, which I recommend as place that is centrally and conveniently located to all the important sights in both Old Madrid and Bourbon Madrid as well as Gran Via. There are plenty of restaurants, tapas bars, mercados, cafes and panaderías nearby and lots of charm. It was a pretty quiet neighborhood even though it was busy. We got a car for our departure to Segovia the night before we left but there are no parking places on any streets as people leave there cars parked indefinitely in case you bring a car. We walked all over the city for 3 days and didn't find any so we found a very small parking garage a few blocks away. Beware of the garage owner, as he has no set price, he just charges you what he wants when he looks at you. He kept changing the price on us.
the apartment is very small, but the bed was comfortable. The shower was very small if you are a bigger person you might have a challenge but it all worked fine for us and we were happy. We don't stay in our place very long anyways because we are out all day walking and exploring the city. It has a great view too! Bring your coffee, tea or cooking oil or condiments if you cook but it has pots, pans and cups. Rather than go to another location to get the key from a locker, maybe leave one with a neighbor?
pros: location, elevator, view, pretty quiet
cons: check in could be more convenient. you have to go to a locker about a half mile away, get the key, but you can leave it at the apartment upon check out. Not much interaction with Juan, it's all self check in.