My wife and I stayed at Ruy's apartment in Monteserrat for 1 week and had a very good experience.
The apartment has a very good location - we had no problems directing the taxi at night and in the day we simply took the subway (within 5min walking distance you will find stations for 2 different lines). There is a supermarket and laundry just below so we had no problems with our daily necessities.
The apartment is kept very neat and tidy by Ruy and the balcony is wonderful to sit, chit chat and have breakfast on.
Ruy was wonderful and offered to give us many tips about the local attractions and even helped us to book a taxi to get to the airport!
Overall, this apartment is very good value for money and we had a wonderful experience here. We will look forward to staying here again if we go back to BA.