Joe,
most of the folk music is indeed in English (as far as I know). There are a few bands who slip in a German song or two, and a few bands who are doing German stuff (often singer-songwriter, sometimes pan-european dance tunes). A lot of Klezmer, if you file that under folk.
PM me when you know exactly when you are coming over and I will try to help you find music and lodgings. Since it is quite a time in the future I can`t promise anything now, but we will see.
Would be nice to meet you!
Ernest