Hi Dana,
You can definitely enjoy fireworks without entering the Disney theme parks.
Wishes Nighttime Spectacular, the enchanting fireworks display above Cinderella Castle is the easiest one to see from outside the parks. You could view this stunning pyrotechnic display from the California Grill restaurant atop Disney's Contemporary Resort, from the boat dock at Disney's Grand Floridian Resort, or from the beach at Disney's Polynesian Resort. If your timing is right, you could also view the Electrical Water Pageant from these locations.
Illuminations: Reflections of Earth, which is shown nightly at Epcot, is harder to experience from outside the parks but I have enjoyed watching the high fireworks of this show from the beach behind Disney's Beach Club Resort & Villas.
Wishing you a Disney vacation sprinkled with extra pixie dust!
Jill
PS. If you wish to dine at Disney's California Grill, you should call (407) WDW-DINE to make advance dining reservations.