I'm going to be in the Ulster/Columbia counties areas myself in Sept and just discovered this great website as I was planning some routes. It has maps, cue sheets, etc.

http://www.roberts-1.com/bikehudson/r/map/index.htm

"I ride up in that area all the time, though a little further east. I would suggest getting a highly detailed map that shows each and every little road, either from McNally, or often they have them up there at B&Bs or gas stations. I would try to avoid state routes (though they are usually not too trafficed) and stick to county roads or smaller. Two things to be aware of: 1) you can stumble upon some really big hills (watch out for road names that include the word ""hill"") and 2) there are many dirt roads, not too bad.
I would recommend heading east, northeast, and southeast from Rhinebeck to find quieter roads, but as long as you avoid route 9 and the other big ones, you should be fine. There is a bike shop in Rhinebeck somewhere, and I'm sure they can make some more specific recommendations.
Enjoy!"

The bike shop in Rhinebeck is not terribly helpful--as of last year they did not know the Roberts' website. The Roberts have a great ride out of Tivoli along the river up to Germantown and back through southern Columbia County farm land is very quiet and beautiful. It is also pretty manageable even if you are not a great climber. The ride east from Rhinebeck to Rhinecliff and then up (south on) Morton Rd eventually parallels the Hudson and is very quiet once you get out of Rhinebeck. This also is rather flat except for a few rises near Rhinecliff. The Grey Fox Blue Grass festival takes place this weekend further north east in Columbia country, so traffic will be somewhat heavier.
The area is beautful though and sufficiently challening to be interesting.

Thanks everybody for those suggestions.

L.

p.s. That website is fab.