Rogerk-
My experience with some guidebooks is that their information is up-to-date...at some time (almost all of the books state "unequivocally" that the aqueduct 'still provides water to the city,' which would've been true many years ago, but no longer "holds water"). They may not have updated from the past couple of years. Segovia has undergone some extensive rebirth. The main street passing under the acueduct is no longer passable by normal motor traffic, and has been replaced with a nice pedestrian street. The monuments, to my knowledge, are not under major repairs (thanks for the info chpdx1!), but my experience has been that if one or two are under repairs, there is still a plethora of remaining sites to visit. I echo chpdx1's recommendation that you stay overnight in Segovia. Having lived there in the past, I recommend a couple of nights, but hey...
There is an impressive array of churches in town, capped off, of course, by the cathedral. I lived on calle San Francisco, which is the street just to the right of Mesón Cándido (under the aqueduct), and have stayed at both the Hotel Acueducto and the Hotel Los Arcos on the road parallel to the short segment of the aqueduct (your city-side window looks onto the aqueduct, especially beautiful at night). I recommend either for comfort and location. Segovia is smallish and you can stay about anywhere and not really be out of the way.
Don't forget the food!!! Lots of it, and it's all excellent!!!
Hidden gem: Don't miss the Iglesia de la Vera Cruz on the oustkirts of town (on the road to Zumarramala). Read up on it in your books...original frescoes on the walls, 12-sided design, beautiful belltower, and loads of history. The area in front of the church became a cemetery during the bubonic plague, and you can see some of the fragments of bones in the courtyard area...
Let us know how it goes!
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Ongi etorri!