Change language layout in screen lock
I have the exact same problem as you and I get around by doing this:
get rid of
gnome-screensaver
by:sudo apt-get purge gnome-screensaver
Install the X screensaver by:
sudo apt-get install xscreensaver xscreensaver-data xscreensaver-gl
Whenever you forgot to switch back to English before the system locks itself, hit Ctrl+Alt+F1 log in as your admin user and kill -9 xscreensaver
and you're back in!
(It's just a workaround and not a real "solution" but it works for me and is definitely better then shutting down and restarting)