How can I prevent the iCloud dialog from showing up for new users?
Solution 1:
From a Terminal window:
sudo defaults write /System/Library/User\Template/Non_localized/Library/Preferences/com.apple.SetupAssistant DidSeeCloudSetup -bool TRUE
Source
From a Terminal window:
sudo defaults write /System/Library/User\Template/Non_localized/Library/Preferences/com.apple.SetupAssistant DidSeeCloudSetup -bool TRUE
Source