THe DEC boat launch is park of the Saratoga National park which does NOT allow ATV's.
But, you may put an ATV on the lake next to the launch at Lee's Campground or South Shore Marina or Fitch Rd. Again, make sure that you have all your paperwork and ALWAYS wear a helmet while ATV is in use, even to move it 10 feet. They (cops) will get ya if not.