Mulan can usually be found at EPCOT in the China pavillion. I've heard she usually appears at the Princess Storybook Breakfast at Norway too, though not usually at lunch or dinner. She's also in the parade at MGM.
None of the Dalmatians appear in the parks, but Cruella can sometimes be found. I've seen her in Town Square at MK a number of times, though not lately. She's also in the Dreams Come True Parade at Mk and Stars and Motor Cars Parade at MGM. As for photo oppertunities, there's some at Town Square near the fire station and in the back of the Expo Hall. You might also want to stay at or visit the All Star Movies Resort. There's a 101 Dalmatian section with larger-than-life statues of Pongo and Perdy.
