Well, I don't know you guys, so I didn't know if you might need or want to go back to the hotel during the day! How was I supposed to know that? So I wasn't telling you about hard it is to drive there because I thought you were staying there with the car, I just wanted to point that out in case you were considering going back to the hotel while you had the car.

I don't think you can get to any of the locations with old windmills without a car (or perhaps tour buses, rather than normal buses), even if that's the only thing you want to see. They are a couple hours south of Madrid on various lonely roads. At one of them (but only at one, and not the best one in terms of authentic age) I saw some sort of tour buses, I presume it's an all-day tour. Some of other locations didn't have places for tour buses even, just a dirt patch to park one or two cars at a time.

So it depends on what you want to see as to how much you need a car.