Just note that it's only available at select locations: Bengal Barbecue, Galactic Grill, Gibon Girl Ice Cream Parlor, Harbour Galley, Hungry Bear Restaurant, Jolly Holiday, Red Rose Taverne, Tiki Juice Bar, Award Wiener, Bayside Brews, Clarabelle's Hand Scooped Ice Creak, Cocina Cucamonga, Corn Dog Castle, Flo's V8, Lucky Fortune, Pacific Wharf, Paradise Garden Grill, and Smokejumpers.
The major/popular ones that I can think of that are not included are Plaza Inn, Alien's Pizza Planet, French Market, Cozy Cones, Schmoozies, Corn Dog Wagon, Rancho del Zocalo, anything in Toontown, and anything in Pixar Pier. Other, like Jolly Holiday, might not have their full menu available. And I've found that you cannot substitue ice cream flavors in the sundaes at Gibson Girl and Clarabelle's.