Going for a week to Portugal in September, as I have a problem with walking, which is the most accessible for visiting sites, beach, restaurants, etc. Is one more hilly than the other?

Hi Rosie

If you have a problem with walking, don't stay in Sintra. You have to climb much as it's a village on the mountain.
Stay in Cascais, it's very easy to accessrestaurants ( you have plenty), beaches, shopping and the train to Lisbon and Belem , where there are many historical sites is just there.
I don't know your budget but if you can afford it stay in Hotel Albatroz, it's lovely, right in the center of Cascais, near everything . If not, Hotel Baia is also very well located.

Have a good time

Teresa

One more thing: Sintra is far from everything and the train to Lisbon is not as good as the one in Cascais. But if you can go there to spend a day and see it. It is worth a visit.

Thanks Tere, most helpful, will also check out the two hotels you mentioned.

You're welcome Rosie.
I live near Cascais so, if you have any more questions or want some sugestions on resturants and other things feel free to email me at [email protected]
I will be glad to help you