We're just back from an 8-day stay at Juan's place and we loved it.
The apartment is roomy enough for two people and ideally located: a 5-minute walk from the Castelo de Sao Jorge, 5 minutes from a very convenient supermarket, 10-15 minutes from the Praça de Figueira, etc...
The street is very quiet and the apartment is cool whatever the outside temperature, which is nice when you want to rest after a whole day spent exploring the city.
Juan is extremely nice, friendly and helpful. Ask him any question, he has the answer! Do not hesitate to visit his small shop too; it is full of surprising and very nice handmade jewels ;)