There are two really good museums in Lisbon that would be a shame to miss. The Tile Museum and the Decorative Arts Museum. It's not every day that you get to see beautiful tiles displayed in a museum. I also enjoyed the monastery in Belem.

You can take day trips to Sintra but I liked staying there 2 nights. There's a lot to see.

Perhaps flying into Porto, seeing the city for a couple of days, renting a car and stopping at a two or three towns on the way to Sintra (Obidos is good for two hours tops), turn in the car and spend a two nights in Lisbon.

Just be prepared for rain. November in Portugal means rain more often than not. Although with the weather the way it is these days, who knows.
If you want to see some of Portugal's beautiful coastline you can do that by driving from Porto to Lisbon and skip the Algarve.
Enjoy your trip.

I would add days to Sintra-beautiful and take the train into Lisbon-too gritty for me-I did not feel comfortable/enjoy walking around-take the on/off bus to get the feel for Lisbon and head back to Sintra to relax! Sintra has great castles and loads of walking options.Lovely little town to wander.

While I would add the days to Lisbon and day trip to Sintra... (and Belem). I'd add the Gulbenkian to the must-see museums in Lisbon, probably along with the Palácio dos Marqueses de Fronteira. You don't need a car, the rail system is fine. You certainly don't need a car in Lisbon or Porto, you can day trip by train or bus, and it would be a real pain in the city.

I, too, would add days to Sintra, especially since you're interested in castles and history. You can easily fill three days if you want to visit them all, and walk all their parks and gardens.
Just like chapla, we also took a daytrip from Sintra to Lisbon. Lisbon is nice, but very hectic, so we were glad to be back in quiet (almost dead) Sintra after our daytrip.

Three nights in Porto sounds good, but could be longer for me. I love this city! Do include a trip (drive) into the Douro Valley, maybe stay a night at a wine estate.

Thanks so much for the feedback. Still mulling the exact days in each, but so far no one has suggested a completely different area at least! Definitely prepared for some rain, although hoping for the best. We like shoulder season travel.

If we ended in Sintra, is it close enough to the airport in Lisbon to be doable? Also, in November, is having a car in Sintra for at least some of the time (for visits elsewhere), still too much of a hassle?

I will look into the Lisbon museum recommendations, and the possibility of an extra night on a wine estate in the Douro Valley too.

If you do want a stop between Porto and Lisbon I'd recommend Coimbra. The old town is fun to wander, the university library is spectacular, and there are good Roman ruins at Conimbriga. It's on the train line.

Sintra is about 40 min. by car to Lisbon airport. I didn't find having a car in Sintra a hassle (we were there in June). It's easy to go to all the places of interest, although there are buses operating but I don't know their schedule. We also took our car to get to the train station in Sintra for our daytrip (by train) to Lisbon. A car is certainly not essential in Sintra, but we also used it for a daytrip to Cascais, Estoril, Cabo da Roca and Boca do Inferno.

For an overnight in the Douro Valley, check out the Quinta do Passadouro in Pinhão. I haven't been there myself but friends of mine have. The quinta is a run by a young Dutch couple who work with all their heart making wine, port and olive oil.

Don't shortchange Lisbon. Take a day trip to Sintra but stay in Lisbon.

Sintra is about a half hour from the Lisbon airport w/o traffic. The problem I had was reading the Portugese signs. There are some signs in English but not all and I didn't know which exit to take off the highway. I had to turn around and backtrack and got confused while doing that and had to get off the highway twice more before I was on the correct road to the airport. Unless you have a translation for the Portugese signs I would not drop off the car the day you are returning home, especially if doing so during the week with traffic.

If you're dropping off the car and then staying in Lisbon for a couple of days then you're fine going to the airport from Sintra. The taxi fare into town is about E10 - don't let the driver overcharge you.

Fill up with gas before dropping off the car. There's a BP in the airport grounds.

You don't need a taxi from the Lisbon airport. There's a perfectly good bus, and the ticket will cover the Lisbon transit system for the rest of the day.

Or else the red line of the metro now goes to the airport.

It seems like Evora is not on your itinerary, but there is a great Starwood Hotel in that city, a few miles ouside the old town. Many very old towns in that area to visit. Under two hour drive from Lisbon.

Reception was waiting for us and we had a junior suite. If you considered this hotel, be sure to stay in the old part and not in the newer addition.

For Sintra, it's an easy day trip from Lisbon.

<<Fill up with gas before dropping off the car.>> Read the conditions first! Europcar, for instance, charges a full tank and you're supposed to turn in the car with as little petrol as possible.

Thanks everyone. We have decided on two nights in Lisbon, three in Porto, and three in Sintra. We'll use points for the Sheraton's in Lisbon and Porto. I am mulling over staying at Casa Miradouro or Lawrence's Hotel in Sintra. Any advice there? They both look lovely.

I think for the most part we will take trains, and possibly rent a car (or even a guide/driver) only for day trips from Porto and Sintra. I need to do some research on these options.

I appreciate all the feedback!

I don't think it would be fair to compare a 4* B&B (Casa Miradouro) with a 5* hotel (Lawrence's).
From the Casa Miradouro, being on a hillside, you will enjoy the most beautiful views, on the castles upto the sea. It's a 10 min. walk (uphill) to the centre. Lawrence's is in the centre of town. It looked a bit dark to me.