Mainz.. Take the Sbahn to Mainz
Hauptbahnhof, then follow all the people. The parade route is only a 5-10min walk from the station.
I'll also be in frankfurt for Fashings this week. Hopefully will also get a chance to meet some Frankfurt TT'ers at the
Friday Drinks 
Just looked at the events for Mainz this week, the big Parade is on Monday. But there are a few smallers ones leading up to it.
QUOTE
The top Carnival events are: The Children's Costume and the „Impressed-Fools"` parades in the Downtown, Gonsenheim, Mombach neighborhoods; the Fassnacht's Fair along the banks of the Rhine and at the Rathaus as well as Gonsenheim's Juxplatz. February 17th - 20th, 2007. The Fools' Guard Parade through the inner City and the Finthen neighborhood parade an February 18th, followed an Rose-Monday, February 19th, by the enormous Grand parade through the City. Rosenmontag in Mainz is a legal holiday, just to prove how serious Mainzer are about their tom follery!