Maria's home is very cosy and her hospitality is very Portuguese - even I couldn't meet her at all (her son was welcoming us) she had thought on us and left some apples, coffee etc. Beautiful humble apartment with nice balcony and lots of flowers!
The flat is not exactly near to the center, it's possible to walk and that's what we did, but if you want to stay exactly in the hearth of Sintra, you need to find something else (and pay double price).
Maria has a lot tourist guides at her home, also some books about Sintra, and her son was very friendly and willing to help and give tips. The stay was very good, just too short!