We wanted to stay near but not in Lisbon and Maria's place was just perfect. We really felt like we were staying with a local and enjoying the true AirBNB experience. Although Maria's English is a bit limited that doesn't stop her trying and she speaks a bit of French also. She is incredibly warm and lovely, hospitable but gives your your privacy and the room is separate enough that you feel you have your own space. Having your own bathroom is a big plus.
As others have said, 8 min walk to the station, trains every 20-30 mins to Lisbon, about €2.90 return and they take you to heart of Lisbon in about 20 minutes.
Carcavelos itself is really lovely with some great places to eat, drink coffee and get fat on Nata's. Neighbourhood feels really safe to walk around, even late at night.
If you are looking for a place in the true spirit of AirBNB, Maria's place provides a perfect getaway.