I want to disable the "download data" capability [for my app] in Organizer. I belive it's a plist file setting but can't find information on it anywhere.
You're thinking of UIFileSharingEnabled, but that doesn't quite stop people, as reported in this answer. That answer also links to an Apple doc that advises creating a custom directory in [app home]/Library/, something like "Private Documents" (make sure the folder name is unique), since Library/ is maintained in backups and upgrades and hidden from the user. See this link.