I use Ubuntu-Gnome 13.04 and I can't change system language. I set it to Polish with "language & regions". It was though because there is no option for adding so i installed:
then i could pick it in "language & regions" and then reboot. However this didn't solve my problem I also change it with gnome-language-selector and still got english.
Please help, because if the language is other than polish i will have to switch back to windows. I like the gnome3.