I have not seen them out in the parks, only in the Bear in the Big Blue House show. You won't get personal time with them there, but you can get pretty close....
Normally, the only time you'll see the Playhouse Disney characters at MGM doing meet-and-greets is if a performance of the show was cancelled or for a special event. Stanley appears every day at Rafiki's Planet Watch at MK though. Olie and Zowie also did meet-and-greets in Toontown for MNSSHP last year as well. As far as parades go, also be sure not to miss the Stars and Motor Cars at MGM. Bear, Olie, and Zowie are in it.