#1 - April 10, 2012, 5:37 p.m.
If you change that, the game won't ever start. Launcher doesn't work.
Unable to play.
There is currently a Locale Selector in the Options --> Account menu. DO NOT USE THIS SELECTOR! This was not supposed to make it into our Beta build.
Workaround - If your game gets messed up because you use, delete your Battle.net folder from your main harddrive/My Computer/ProgramData folder.