The flat is very well located: 20 minutes by walk to the main square Puerta del Sol so you don't need to take the metro to visit the historical city centre. By the way the metro stop is very close and is in the zone A so the tickets are not expensive. In the streets around there are lot of services ( e.g. supermarkets, bar, restaurants, shops, hair dressers). The room is quite small and silent, well equipped and full of light from the street.
Maria is a kind person, she runs around all day long because of her job but she can find time to receive you and explain you lot of useful things to start your life in this big city.