We were at DW in October and we saw Lilo and Stitch at the MGM Animation Courtyard and also at AK at the Island Merchantile, right at the entrance of the pathway that leads to Camp Mickey-Minnie.
Lilo and Stitch can usually be found at MGM next to the Animation Tour, at AK next to the bridge that leads to Camp Minnie-Mickey, and sometimes after the Castle Show at MK. They're also in the Parade at MGM as well.
Ditto on AK and MGM location. We saw Stitch in the Main St. Circle in MK and at the Castle in the late afternoon in Feb. Stitch is very popular and fun to meet. You should not have any problem finding him.