We throughly enjoyed staying at Javier's apartment, the location is fantastic! If you want to be in the centre, close to the cathedral, stunning architecture and tapas restaurants it's perfect for you. You don't need a car as it's a city to explore on foot.
As Javier points out, there are 3 flights of stairs which are challenging, and only a handrail for the bottom 7 steps. If you're ok with that it's fine.
Javier is a charming host and a very good communicator.