I am in the planning stages now for Portugal, 2 weeks, end of February, first part of March. We likely will use a car for part of the trip, our time may be more limited than yours, but here is what I am seeing.
Nearly all of the towns mentioned in the Rick Steves book (and most others) seem to be easily reachable by bus or train, but a car, for us, will allow more efficient travel some decision points for us:
- We will be stopping in Evora, but will spend the night in Monsaraz before heading to the Algarve, probably not doable by public transport, or at least without having to add a day.
- In the Algarve, we are staying 3 nights in Loule. This will coincide with Carnival, enjoying that each night, but allow us to explore the coast from Loule.
- After that, we are heading North, the car will allow us to hit smaller towns in Central Portugal, then to explore the Duoro valley a little bit. in the time we have ~4 Days for that segment, we would have to pick 1 or 2 stops if using Public Transport as opposed to adding in another quick stop or two, or driving through the smaller towns.
Overall, we will have the car for about a week of the two. It does not appear that we will have an added charge for picking up in Lisbon or Evora and dropping off in Porto. Still working out insurance, there are Tolls, but most rentals make the electronic toll pass available, and the general response from others on here is that driving in Portugal is pretty stress free.
Might add that I rarely rent a car in Europe, Ireland and rural UK were the exceptions, but it does seem to make sense for this trip. If I had more time and was looking to spend larger blocks of time in a number of spots, then I would probably opt for public transport though. We are doing Lisbon and Porto at the beginning and end of the trip to avoid having a car for those segments.