I don't think you mentioned when you might be here. If it's in the summer, there's a hiking trail that runs very near the top of Buttermilk Falls in the Catskills less than an hour north of the Gunks. From there you could theoretically do 5-7 raps of 10-20m each down the waterfall canyon. Then you get to the bottom and you're on the wrong side of Kaaterskill Creek (no bridge to cross) so some wading would probably be required. A few minutes up a slope and you're at the highway, but your vehicle is likely to be a few miles away. The waterfall is a popular ice climbing destination in the winter but I doubt you'd see anyone in there in the summer. Also, there are no fixed rappel anchors - you'd be using trees, some of which are far away from the drops so you'll need a longer rope (maybe 50) than the short raps would suggest. It is not a "trail" and I would recommend that you treat it as a serious canyoneering outing. But it would probably be a lot of good, wet fun.