I always have to laugh a bit when I see advertisements for computers loaded with Windows that can dual-boot (!) both English and Dutch versions of Windows. One of the greatest advantage of using Xubuntu (or Ubuntu, or whatever) is that it is easy and, no less important, free of charge to use it in different languages. In fact, you can use different languages on a per-account basis!
To set it up, you just have to open
From there, you can browse through a list of supported languages. I personally prefer British English (which I also set as the default language in the drop-down menu at the bottom), but my sister does not speak English and therefore would like to use my system in Dutch. No problem, I just scroll through the list, select “Dutch” and check the checkbox under “Support”. Now I can click “OK”, upon which it will download the selected language and set it up. And if you later install other applications that have been translated to the other language, that other language will be automatically installed with it.
To set Dutch as the default language for my sister, at the login screen, she can just choose “Dutch” as the language, then when she logs in she will be prompted whether she wants to use it as the default language or just for that session. (Note: depending on the version of Xubuntu, or Ubuntu, you use, a “Languages” button might not be available. To access it, you first have to select Options and then Languages.)
Unfortunately, translating every single piece of software is a huge job, mostly done by volunteers, so not everything will be translated. But the most important software has mostly been translated, and using a partially-translated operating system is already way easier than using one in another language.