Marta's apartment was wonderful. It was my home away from home. I got to Look soon too early, but Marta and her mother did everything to help me out dropping my luggage 4 hrs before check-in. Marta kept in contact with me (WU) in case that I needed something. The apartment was immaculate and very nice. WiFi was great, water pressure a blessing!!!! and the location of the flat was perfect because it's very close to the metro station called Independiente (Green Line) which would be your stop if you decide to take public transportation; in addition, it's about 10 minutes walk to the historical part of town.
Definitely, if you are like king for a place to stay in Lisbon, do not hesitate staying at Marta's flat.