Comment 4 for bug 1276072

What makes you think that lightdm has anything to do with it? Actually, lightdm is not involved at all when you set the language from Language Support. L-S calls accountsservice, which both saves the language as an accountsservice property and updates ~/.pam_environment. This should work the same way in Ubuntu, Xubuntu and Lubuntu.

If you have studied the ~/.dmrc file, I can tell you that lightdm does not use those settings since accountsservice is installed.

This bug report can be changed to whichever package is affected, so don't file a new report.

But before you change that, let's try to figure out what the real problem is. It would be valuable if you could provide a detailed step-by-step description with the steps you take and your observations.