Localisation should be a matter of convenience
, not of understanding.
If you are really unable to understand what is going on because something is in English, then sorry... but this is as if a blind man was attempting to drive a car.
You cannot possibly develop software or study computer science (or be active in any other scientific area) without sufficient skill in English. Seriously, a good Enlish course is the best investment that you can make. Most technical documentation and almost all scientific papers are in English (as is most of the Internet), and it is not a particularly complicated language, either.
Personally, I don't like localised development tools. These confuse the hell out of me. Not only are many translations really pathetic (quite often, they make you shout "what the F@~* is this supposed to mean!!!"), but your brain has to switch between two languages all the time, which is tiring. Certainly, other people have different preferences, but like I said, this is a matter of convenience
For me, localised versions are acceptable (and desirable) for example for a word processor or for a window manager, because you usually write your letters (or work, in general) in the same language. Also, most "everyday" menu items are not technical terms from CS, so the overall risk of incomprehensible translations such as "Laufwerk aushängen" or "Automatische Eingabeaufforderung für ActiveX-Steuerelemente" is not too great (I have to read this five times to understand what it's supposed to mean...).