Don't know about classes in English, but my practice just recommended
www.hebammen.de to find an english speaking midwife. She also suggested having the midwife come to your house to do the class there in english. I would prefer to do a public class, to increase the chances of meeting people. My german is decent and I'm counting on my husband to translate when necessary. Here's the address of my practice
www.hbamme-hh.de