Comment 1 for bug 873710

Same here, it appears to be a feature of lightdm-gtk-greeter, and unity-greeter does not support it. Adding show-language-selector=true in unity-greeter.conf does nothing.

This is a necessary feature for some users. My desktop is used by two users, one of whom types on QWERTY and one of whom (me) types on Dvorak. The inability to select the language in the Unity greeter for entering the password will make it impractical to use.