The calendar may not read "Dec. 25" yet, but Orlando's great theme parks have made out their lists and checked them twice and are festively decked out for the holidays from mid-November on, with 70-ft. tall Christmas trees, miles of garlands, and millions of twinkling lights and poinsettias. Why, there's even a chance of "snow flurries" at some of the parks --the magical kind that does not require wearing boots, mittens and heavy coats.