Where in the interface is the option to switch regions in Diablo 3?
As I understand it, you have to start with fresh characters. Does this mean you log in to a region or can you switch while in-game?
You can change region before logging in. Look into Account tab, inside Options menu.
As you said if you want to change region (this feature is available when all region has launched the game) you have to start a fresh character and you cannot do it "on-the-fly", but you have to exit and re-login.