Is Sintra a good place to stay for a 10 day trip?

Sintra is in the foothills outside of Lisbon.
While it was a resort for Portuguese royalty trying to escape the heat of Lisbon, it is NOT on the coast, so there are no beaches at Sintra.
If you were thinking of a beach town near Lisbon, check into Cascais or Estoril.
The Algarve coast is where most travelers looking for a beach holiday in Portugal go.

agree with what kenko says - however still try and get to Sintra for a day or two - pretty awesome place

As above. Sintra is a very worthwhile day trip; you could even stay overnight and make 1½ days of it. But there's certanly not enough to do there for ten days. And it isn't on the coast.

We stayed in Sintra for two nights in 2013 and it was one night too many.

Place to visit, but not one for a long stay.

If you've seen a reference to the toy musuem in the centre of Sintra, please note that it closed in 2014.

So would Cascais/esterol be a good choice for a 10 day stay? The Algarve is packed, we can't find accommodation there. Looking for something a little more laid back anyway. Are the beaches nice in Cascais and esterol? Should we rent a car? Are there places to stay right on the beach?

Cascais and Estoril quite close together and there's easy rail acess to Belem and Lisbon plus bus access at least to Sintra. Few recommendations for Cascais re; family destinations on here in recent months.

Plus comments in our car about and hour ago about my partner heading over there with her daughter, son-in-law and grandchildren at some point.

We haven't hired cars in Portugal as we've used buses, trains, Metro and other forms of local transport to get around in each of our four visits since 2013.

How are the beaches in Cascais and estoril? We're coming all the way from the states, is this a good choice for a 10 day stay? I like to proximity to Lisbon, i don't relish a 4 hour car ride to the Algarve but I want beauty and culture. Is Cascais and estoril a good choice for beaches and culture?

Some comments on Cascais on here;

https://www.lonelyplanet.com/thorntree/forums/europe-western-europe/portugal/two-weeks-in-august-with-kids-suggested-itinerary?page=1#post_22108599

https://www.lonelyplanet.com/thorntree/forums/europe-western-europe/portugal/3-months-in-lisbon-area?page=1#post_22071533

https://www.lonelyplanet.com/thorntree/forums/europe-western-europe/portugal/best-home-base-for-three-months?page=1#post_21954321

Hope that these help in some way...

Great information, thank you. Does anyone know if there is lodging in Cascais on a sandy beach? Resort, hotel, condominium, apartment, anything really. As long as we can easily walk to the beach with the little children. I'm not finding anything on booking.com. Too bad you can't search by beachfront.