I very strongly suggest a couple of nights in Sintra, a very magical small town destination outside of Lisbon. I have been to Cascais a couple of times too, and though it's pretty nice I prefer Sintra. Hotels in Cascais are overpriced and still grungy, since it's a seaside town. We saw rowdy groups from elsewhere in Europe, kind of like you would see in Prague. Maybe it was a soccer weekend but it tempered the appeal. Visit Cascais, but don't stay there is my advice. Portugal is a country where it makes sense to pick hotels carefully, and even to pay a little more. The standard is lower than in most other countries in Europe. We paid $140 a night in September 2008 in Cascais for a place with gross stains on the carpet. We tried to ask for another room but they told us nope, they are pretty much all that way. We also had a clunker in Tomar, found in the Lonely Planet Guide. You can get your beach at Nazare, don't have to go all the way to Lagos. I have read that the charm of Nazare has eroded with more visitors, but in 2008 it was spectacular. Algarve can be very tourist trap-like from what I have read. Obidos is a must as a day trip. Tomar is a great stop too (for the castle/monastery), as is Evora, though a little out of your way on the north/south corridor. Also, better to end in the big city of Lisbon rather than starting there.
