The observation deck is at the opposite end of the building from Chef Mickey's, on the same floor. Just walk away from CM, all the way to the other end of the concourse. You'll find a door that leads outside. The deck is under the monorail beam, and you'll have a nice view of Wishes.
This is the only viewing area for the general public at CR. The deck outside of CG has a spectacular view, of course, but they won't even let you on the elevators to that floor unless you're dining at CG.