After re-installing Ubuntu 13.10, the Vietnamese input settings in iBus changed. Before this it used the telex input method (same as Android and iOS defaults). Now it has a very strange keyboard with the diacritic accents replacing the number row. I would like to use the standard telex method if possible because the new layout is very bizarre and also makes it impossible to type numbers without switching back to English temporarily unless one has a numeric keypad.
Try to install
sudo apt-get install ibus-unikey ibus-daemon -Rd im-config
im-config you choose IBus as the default input method.
Require to have language Vietnamese installed - a good guide as detail here to do so
After that open System → IBus preferences and add Unikey to input methods.
Finally, add Vietnamese keyboard in System → Region & Language and then you have telex your own.
This works for me with this guide.
Install & restart
sudo apt install -y ibus-unikey ibus restart
Then, go to Start menu → Text entry settings → add Vietnamese (ibus).