Does the Amhric language need a special font installed? Can it be represented in Unicode? Do you want to serve an Amhric page to people physically in Ethiopia, and an English page elsewhere, or do you want to serve an Amhric page to anyone who can view Amhric, wherever they are in the world? Basically, what are the conditions under which a browser 'has the Amhric language'?
Either way, that is, even if you find it's possible to do this ( which it might be ); I would certainly do as MidiMagic said, put a link saying 'English' or a frontpage saying 'Which language would you like?'.