Cannot change users in Google Play Services from within C2 game. Not sure if this is a bug in google, C2, or just no provided ability to change users with the API.
Steps to Reproduce Bug
Sign in as a user. Sign out. Attempt to sign in again, and it remembers the last user. So user cannot be changed. Only way to change user is to sign out from a different google application / google plus.
When signing in, should be able to input user credentials.