In WDW you can meet him next to his attraction in Fantasyland.
In Disneyland Peter does often come out to play, but it is never guaranteed you will find him. The best place to look for him is at Refreshment Corner on Main Street, or wandering around Fantasyland.
At Disneyland Paris Peter usually appears near the pirate ship in Adventureland.
In Tokyo, Peter is often out in Fantasyland.
Peter does not meet in HKDL.
Peter does appear on select Disney Cruise Line sailings. Check your Personal Navigator for details.