If you are like my family and wanted to see downtown Lisbon as well as Belem area, the Alcantara neighborhood is the best place to be. Tiago's apartment is perfectly situated to do both visits.
We were a 15 minute walk to Alcantara train station and bus line was extremely close too. Even taxi station was very quick walk for us. We took a taxi to Sintra which was 35 euros for all 4 of and saved a huge amount of time and hassle.
I think we were lucky to get this apartment so if it's available it must be reserved.