Looking for advice on a 12 day itinerary in early May.

You didn't state (nor do most OPs) whether your travel period, twelve days, includes the day you fly in and the day you fly out, but I'll assume that they do; so before alternative itineraries are proposed below, I'll point out that the one you proposed looks feasible. You will have eleven nights in Portugal, enough for one night in your arrival city after landing, another in your departure city before returning home, plus your proposed three nights in the Douro Valley and four nights in the Algarve. This leaves two nights more, which you can add either to Lisbon or to Porto, even though both cities merit longer visits. Also, I'm assuming you can go by train from Porto to the Algarve in one day, though I haven't actually attempted it yet. (Keep in mind that Portugal is just slightly over half the size of new England.)

I wouldn't be adding this if you hadn't asked for our "dream trips," but since you did, mine would be a train tour through as many of Portugal's many quaint, historic, but less-visited cities as I could fit in -- examples would include Viana do Castelo, Guimarães, Coimbra, Guarda, Tomar, Evora, Beja.

I would not recommend trying to do all that in only 12 days. Drop the Algarve and focus on Porto, the Douro, Lisbon and a place or two in between.

The Douro is lovely and all the towns are small. The larger ones are Pinhão and Régua. Staying in a wine Quinta is a great experience even though there won’t be much action with the grapes at that time of year.

Is you want beaches, there are a number of small towns in the Silver coast area with lovely beaches. But, having a car for that area is best. The roads are easy to drive and not congested.

Batalha and Alcobaca are quite interesting with loads of history. Coimbra is also quite nice.
Do a bit of research on the silver coast to see what interests you. The Algarve is really mostly about beaches. Not much else of interest IMO.

Thanks Faedus, I did mean 12 nights. I booked my flight yesterday, arrive on a Fri at 10 am to Lisbon--my daughter may not be able to meet me until Sat. We'll probably stay in Lisbon area until Mon and then head out to Porto/Douro.

Kathrynnj--thanks for the advice on the Algarve--we are not huge "sitting on the beach all day" folks, though we love a good seaside view and the caves and natural features look beautiful. My daughter has the Algarve on her wish list as when she first visited, she spent all her time in the cities of Lisbon and Porto and surrounds, and wished she saw more, so I will discuss it more with her.

Looking forward to researching some of the towns/cities that you and Faedus have recommended. Maybe we'll chose one or two for a stop over.

I agree. Coimbra was a surprise highlight. A very old university. The library awash in gold.

I basically agree with kathryn, above: I, too, would not have wanted to do your itinerary in just 11 (or 12) nights, though i did think it was feasible. If your daughter really wants to see the Algarve, however, you could probably add one or two nice Alentejo towns as well, such as Evora or Beja (I haven't seen either yet; I've just heard they're nice.)

portugal is very doable in 12 days by train and bus, but to avoid feeling rushed, I recommend flying into porto and out of lisbon. start with 3 nights in the douro valley for that countryside fix, then head south with a stop in evora for incredible roman history and art before hitting the algarve. the alfa pendular high speed train makes the long trek from north to south easy, but you will definitely want a car for just 2 or 3 days in the algarve to reach those tucked away sea caves and clifftop trails that buses often miss.