We are in the process of organizing a trip to Portugal starting May 10th with a week in Lisbon. We plan to pre-book accommodations in Lisbon and Porto. But do we need to pre-book other accommodations or can we make last minute choices? Most the touring trip will be covering the Alentejo and Algarve, but we plan to spend a couple of days in Nazares on our way to Porto.

It's always best to have reservations. Waiting until the last minute to find a place to stay means that you will be paying more, generally a lot more, if there is availability.

The last time we traveled in Portugal it was in June and we had no problems getting last minute hotel rooms, even at a discount at the two pousadas where we stayed. Would the month of May offer similar conditions?

Why would it not - May has fewer travelers...?

Honestly I would try to lock in a room that you can cancel without penalty. May is one of the best months to go to Portugal (not as hot as later in the summer) and since there are so many cheap flights within Europe, as well as cruise ships, it will likely still be packed. I could not believe the crowds in October.

That said, there really was no shortage of hotel rooms in Lisbon (I didn't go to Porto), but if you have preferences or a tight budget you may want to book now.