Is there is a way to delete visitors, etc. that were added for testing/training purposes in PassagePoint Global?

You can use the "Reset" Button, located at:   Home> configure system>system administration> Database tools> next to Reset Database> Hit "Reset". This action will remove all the records in Passagepoint.

The Reset was designed to remove test data. If you need to remove data once you have the system in production, do not use the Reset Button as it will remove all visitor, directory, and watch list data.