Turning off the screensaver for users is easy enough to do from System Preferences however this has no affect on the screensaver that is activated when users are logged out of the system and the machine is left at the login screen. Disabling the login screensaver needs to be done at the command line with the following command.
sudo defaults write /Library/Preferences/com.apple.screensaver loginWindowIdleTime 0
The com.apple.screensaver.plist file will likely not exist until it is created with this command. It will go into effect immediately.