Garbiñe's place is very well located: walk between the house and La Latina metro (3 minutes) for the best adresses, nicer than the way to Tirso de Molina even though this one is to try as well!! We did not speak spanish enough but if you do you will enjoy lots of theaters and shows outside. It is at a walking distance to all center of Madrid. The area is very safe, even though the neighborhoud can be a bit dirty sometimes.
About the apartment in itself it was perfect. As in the pictures (except the couch that has changed for two perfect rocking chairs!), incredibly good temperature (whether it's hot or cold outside), everything to heaten or coolen the air if needed (but we didn't in the whole month of May), it is very well equipped. It is at the 4th stair without elevators but you get used to it and it helps you stay healthy despite all the fried food in Madrid!
Also quality/price ratio is absolutely excellent. If this flat is free on your dates, don't hesitate.