I can confirm having similar issues with signing in or out of iCloud on both iOS 9 and OS X 10.11 beta. I am unable to sign out of iCloud in System Preferences on the Mac, and unable to sign into iCloud on iOS9 beta on an iPhone 6 Plus. I ended up creating a new Administrator account on the Mac and have resigned to remain signed out of iCloud until the next beta update, which hopefully addresses the issues.
Topic:
App & System Services
SubTopic:
Core OS
Tags: