In the US parks it is very rare to find Captain Jack out meeting guests. He has appeared at the Halloween parties at both Disneyland and Magic Kingdom until last year (and indeed the Christmas party at MK), and hopefully he will continue doing so.
If you are willing to travel outside the US your chances of meeting Jack increase greatly. He has a regular Meet and Greet on the Caribbean Disney cruises.
In Tokyo you can sometimes find him in both Adventureland near the Pirates attraction as well as in DisneySea around the ship located in the Fortress Exploration in Mediterranean Harbor