I experienced this issues as well. The EULA is presented if you launch Forms Central before the main Acrobat XI application. I used an application called installwatch to identify a file is created in the userprofile when you accept the EULA via Forms Central.
If this file is included in your deployment then it will suppress the message in the event Forms Central is launched first.
The file is called eulaAccepted without a file extension. It is a zero byte file as it contains no information. It is essentially a flag file. This need to be placed in the roaming profile location %APPDATA%\com.adobe.formscentral.FormsCentralForAcrobat\Local Store
For example:
Windows XP:
C:\Documents and Settings\USER\Application Data\com.adobe.formscentral.FormsCentralForAcrobat\Local Store
Windows 7:
C:\Users\USER\AppData\Roaming\com.adobe.formscentral.FormsCentralForAc robat\Local Store