After seeing Lisbon we plan to train to Porto stopping for two nights in Coimbra. We are considering renting a car in Porto and driving to Braga and spending the night in Guimaries. Then we would drive onto the Doro River Valley.
1. is that the best way to see Guimaries And Braga or should we train there from Porto.
2. does anyone have a suggestion for a hotel in Guimaries?
3. after the Duoro River Valley, we plan to drive to the coast near Lisbon, maybe Cascais??? And use that as a base to see Sintra,, Estoril, etc.
thanks so much for your suggestions. I’m trying to move on with this because hotels are getting crowded for May.

1. It's really quite a bit much to do real justice to Braga and Guimarães on the same day and especially by bus or train. It's just too much, or it is for me. I would choose either or (my vote would be for Guimarães, a UNESCO World Heritage Site, or...simply.take a small group tour from Porto that can combine the two, along with the staircase of Bom Jesus do Monte, as the small group van tour can maximize your time, such as this one.

2. If you train to Guimarães I would stay in the historic quarter at the former Pousada, now turned contemporary hotel, the Hotel da Oliveira

3. I'm a big fan of seaside, very pretty, manicured, mansion-filled Cascais with 3 urban beaches, and I've used it as a 3-night base to visit the monuments of Sintra and a walk out to Guincho and a 3-kilometer promenade walk (called the Paredão) to Estoril (very walkable in about 25 minutes).
But I wouldn't just spend one night in Cascais and hope to see Sintra properly, as Sintra is now just too busy, too crowded to do it justice in a day, if you hope to see 3 of the 5 now monuments, then move on to Lisbon on the same day.

Many, many people do the Sintra day trip from Lisbon on the suburban train and spend the day, usually being able to manage 3 monuments but not all, due to the crowds, but from Cascais you would want to take an Uber, as the Cascais-Sintra bus gets very crowded and is slow, then you would want to Uber from there to your Lisbon hotel. I would never take a car, as parking is at a premium near the train station (although people do find parking spaces there), plus the central historic quarter of Sintra does not allow private vehicles, just the local buses, Ubers and tuk tuks and there is no public parking in the Parque de Sintra.

We were so happy that we spent several nights at the city center Pousada in Guimares. It was a highlight of our time in Portugal.

Last year my cousin and her two grown daughters did a quick 6 night trip to Portugal, splitting their time between 2 nights in Lisbon, 2 nights in Sintra and 2 nights in Cascais. It worked well and they traveled exclusively by Uber from place to place. So that is only seeing a small area of Portugal but they had limited time because of the way the Feb school break fell.

There is the Pousada that sits high above the city and the former pousada in the historic quarter that is now the Hotel da Olveira, no longer a Pousada. We stayed in the former, which is a magnificent former monastery and now a Small Luxury Hotel, but for just 1 night, I would stay in the center, which is much handier. We had 2 nights there.

To give you an idea of what Sintra is like these days, you might want to check out 3 trip reports, by maitaitom, progol and melnq8. Just scroll down to their Sintra stays to give you an idea. These are great trip reports of their lengthy travels through Portugal. You can learn a great deal about travel through Portugal by reading these detailed reports.

Falling For Portugal: A Mai Tai Tom (Trip) Report
Portugal at last!
I left my liver in Lisbon

We really enjoyed our time in Guimaraes and liked the Hotel da Oliveira a lot. The staff was lovely. If you stay there, please ask for a room facing the Largo da Oliveira (the large square) and NOT the street. On our first night, we had a beautiful room overlooking the street but there was loud music from a club nearby that went on late into the night (and morning!). We were moved to a room facing the Largo and it was so much quieter as well as fun to watch the evening activity in the square.

Thanks so much for your thoughtful replies I will take your advice and do only Guimarães and spend the night at the hotel . Oliveira.
also, we will plan to spend three nights in Cascais or nearby. Thanks for the suggestions of using Uber for transportation.

Should we consider dropping our rental car off at the Lisbon airport on our way south from Porto and just use Ubers, etc. to do the coastal region?

Ubers worked fine for us on the Estoril coast. We didn't have any cancellations (as some have reported here) but we were there in March, before the high season, not in May.

A Cascais-based poster on the Rick Steves Portugal forum, whom I follow, uses an Uber or Bolt to move around the coast, as she doesn't drive, and the buses do get very crowded and make many stops.

Our hotel also called for a taxi for us on one occasion to dine in the "hinterlands".
We took an Uber from Lisbon to Cascais because we wanted to be "car free". We also took an Uber from our Cascais hotel to the airport for our return to Spain.