Here is some information about Growl and CS5. http://kb2.adobe.com/cps/840/cpsid_84093.html
Adobe Application Manager Enterprise Edition (AAMEE) for CS5 will have the ability to not install Growl on client machines. AAMEE is the CS5 version of the CS4 Deployment Toolkit.
AAMEE will be available as a free download on May 28th 2010. There is a check box to disable Registration in AAMEE.Disabling registration will prevent Growl from being installed.
Thanks, Adobe CS team