Sintra has two centres. The centre historic is very busy and tuk tuk taxis everywhere. We preferred Sintra San Pedro which is much less touristy and we found lovely restaurants and bars and cafe. One had some live jazz in the square and we passed a happy hour or so listening and drinking super bock.
You can walk to the moorish castle on the hill. It's a bit of a climb or take a tuk tuk. The views to the west and north are amazing if you have a head for heights.
We visited all the beaches and found Ursa near Cabo de roca to be amazing and totally unspoilt. The path to the beach took 30 minutes and was a bit hairy with a bit of on all fours in places but not scary. Clothes seemed to be optional on the beach.
It was a lovely stay. Carlos has four dogs but they were no problem. The dog next door to the chalet was a bit noisy though and sleep was not entirely undisturbed.