Walter L. Rubens, former owner and general manager of radio station KOBE/KOPE in Las Cruces, N.M., and a member of the Associated Press board of directors, died Monday Sept. 23 after a long illness. He was 75.Rubens was appointed to the AP board in 1976, one of the first broadcast members with full voting power. At the time, he was president-elect of rhe Associated Press Broadcasters Inc. He served on the corporate board until 1979. Rubens also was a member of the New Mexico Broadcasters Assn. and was a director of the New Mexico State U. Aggies Sports Assn. He is survived by four daughters, a son, six grandchildren and a brother.