Since this is a frequently asked question on this board, I thought I would post a "review" of my car rental. I recently rented a car for a week in Lagos, Portugal. I got it from Luz Car (luzcar.com) For the last week in April I paid $160 Euros for one week, inclusive of all insurance. I got a Ford Fiesta which was almost new. Great car. The staff brought the car to the hotel I was staying at, and came and picked it up a week later. It was a perfect rental experience. I would highly recommend this company if you are in the Algarve, they have offices in many towns. Rates will differ.
Be aware of toll roads! I drove all over the place and was a little surprised how expensive gas was, and how expensive the toll roads were. It cost me $23 Euros to drive from Portimao to Evora, and $9.00 Euros from Evora to Lisbon. Then there was the bridge....I sure goofed on that one. I had a hard time understanding what all the signs meant and I was in the wrong lane. Stay to the right. DON"T go through a toll booth with a green V - kind of looks like a backwards check mark. That is Via Verde and is for prepaid tolls. Most tolls you can pay at a post office 48 hours AFTER you go through a toll booth, and pay the fee. The bridge is another story.. Haven't figured that one out yet! It is a completely different story, and after you Lisbon it isn't easy to pay a toll for the bridge.