On Christmas Day Miss Bonnie Behrens became the fiancee of Rick Kurtz according to an announcement made by her parents, Mr. and Mrs. John Behrens, 725 Range Line Road, Kohler.The couple is planning a wedding in 1974.Parents of the future bridegroom are Mrs. Lorraine DeRuyter, R. 2, Sheboygan Fails, and Gustave J. Kurtz of Salem, Ore.A senior, the bride-to-be is attending Sheboygan Falls High School. Her fiance is a 1972 alumnus of that school and is a mechanical engineering student at Lakeshore Technical Institute. Mr. Kurtz is employed at Curt G. Joa, Inc., Sheboygan Falls.