Not a NYer, but my uncle ran a rather spiffy (over 800 acres) standard bred race horse farm less than 15 miles from there, in Wallkill, NY. During grade school and high school, I would be sent up in the summer to spend some time there. Sadly, I wasn't biking then, but did spend some time hiking an bouldering on Mohonk property, and swimming in Lake Minnewaska (always cool, to downright cold, even in summer).
FWIW, there used to be a competing resort to Mohonk on Minnewaska property, run by the Mohonk owner's twin brother. More here:
http://www.nytimes.com/1987/06/03/ny...ar-battle.html
If you are around mid-summer, cruise on over to Sams Point with a small bucket for a nice haul of free, wild blueberries.