Can I install additional languages on Android?
Just search on the Google Play store for "custom locale",
there are a couple of apps that will allow you to install a LOT of languages.

I tried many times on different devices and Android versions, sometimes some menus or apps do not change the language, but on average it's OK. 

Example applications in Play store:


MoreLocale 2
Set Locale and Language


But there are many more...