We staid at Dagmar's place for a few days with my parents and girlfriend to explore Sintra. The place is amazing: spacious, bright, cozy and really clean.
Dagmar was really helpful and responsive. We requested to checked in late which was not a problem.
The house is located in a quiet street and there is a little alley where you can park for free. It is about 15min walk to the historical center. It is fairly hilly but doable. Public transport should take you there faster but we preferred to walk.
I highly recommend a stay there. We will stay there again if we have a chance.