I did this once to facilitate my learning of Swedish. Guess what? No go.
Reason #1: Mac OS is very shortcut driven. This is a great advantage it has over other OSes in every aspect, except language learning. I know all my shortcuts. Those that I don’t, are intuitive enough to figure out. So I rarely see the menus.
Reason #2: It’s really frustrating when you need to get something and you cannot figure out an alert message. Granted, this happens very rarely, but when it does, it can drive you nuts.
Reason #3: Shortcuts, again. Some of them don’t work (either because the keyboard layout changes, or because they’re programmed differently). Can also drive you nuts, especially, if it’s basic stuff you use ten million times a day.
Reason #4: Sorting options. You can leave them in English in the Finder, but some apps are affected.
Reason #5: Also pertains to lists. Spotlight is smart enough (usually) to find the correct item, based on it’s English name, but navigating in the Finder is hindered significantly. For example, if I need to look for something in ~/Library/Images, I’d normally hit Command-Shift-H to go home, then “L” to highlight the Library folder, then Command–Option–Down Arrow to open it (and close the parent folder), then “I” to highlight the Images folder, then Command–Option–Down Arrow again to open it. Now, the entire drill usually takes less than two seconds. When I switch the UI language, the names of some system folders also change (also, then names of some apps change). You can imagine what follows . . .
This is not to discourage you from doing it. I just thought you’d want to be aware of those things early on. Maybe knowing them will prepare you, and, learning from my mistakes, you’ll be able to get much, much better result with your “geek immersion method.”
Good luck, man. Seriously.
P.S. Guess what the About This Mac item in the Apple menu changes to in Swedish. Literally, it reads “Of this here computer.” Cheers.