I don't imagine Mikes Bikes or any tour companies will be hiring guides any time soon. I work for Munich Walk Tours and we definitely are not hiring anymore guides until around April 2007 in preparation for the high season.
Check out EurAid. It is a travel office that assists English speakers, German not requisite. I believe I saw an ad in their window recently. They are based out of
Hauptbahnhof. Alternatively there are a ton of international companies headquartered in Munich. Start inquiring with them. These big companies tend to have a travel office in house.