Aladdin is probably the most consistent of the Disney Princes / Heroes in terms of meeting him.
In the Magic Kingdom he is always next to the Magic Carpets in Adventureland. In EPCOT he can usually be found at Morocco.
At Disneyland he can usually be found at Aladdin's Oasis in Adventureland.
In Disneyland Paris, he can usually be found at Adventureland Bazaar.
In Tokyo, he is often out in Arabian Coast.
He does not meet in Hong Kong, currently.