The apartment is very well located in the Chueca neighbourhood. The metro is also very close and it's easy to get around. I would avoid coming by car at all costs! There is practically no available parking around. It took us 1 hour to find a car park on arrival to Javier's apartment.
The apartment is perfect for 2 people. It would be ok for 3 people but I don't think for 4 people, unless you are very good friends/family and its a short stay.