If you're staying for a few days in Porto, a trip by train up the Douro Valley is worthwhile, especially if you combine it with a boat trip too - Pinhao.
If you partake, port wine lodge tour is one to consider. We took the cablecar down to the riverside and went around Sandemans.
Pocket Rough Guide Lisbon covers the city plus Sintra, Cascais and Estoril.
We spent time in Vianna do Castello last year and Aveiro. Spent two nights in each and used trains to get to both. Long walk to and from station in Aveiro though - canal boat trip was touristy but fun. Aveiro Rossio Hostel was fine place to stay - best hostel that we've stayed in in Portugal. Had a double ensuite.
Hope this helps...
Some pics in amongst this lot taken in the last year.
More ramblings about Portugal on there too - click on Portugal to the right of the screen (newest postings first, oldest last).
https://wisepacking.me/2016/05/26/one-year-the-answers/