We stayed at the top floor of the Calcada Santana appartement for 7 nights. The apartment is clean, spacey enough for two persons, has a fully equipped kitchen (eating out every night can be quite expensive) and has fast working wifi! We met Carlos, Pedro's father, who showed us around and suggested some activities and bars to play our music. Very helpful.
Apartment is centrally located. Easy to walk to anywhere, although I can imagine that for some people the climb can be quite challenging. But that goes for all of Lisbon, I guess.
One final thing: we would really suggest trying the wonderful cuisine of Terras Gerais Bistro, located a little further down the street at no. 70. You won't be disappointed. The caipirinhas are the best!