Taking their battle for union representation and improved health care to the state capitol, workers at the a Riverside County, California casino owned by the Agua Caliente Band of Cahuilla Indians testified yesterday before an Assembly subcommittee. According to the workers' testimony, the health insurance plan provided by the Rolling Hills Casino is so expensive that they have been forced to rely on state health-care programs for the poor---allegations vehemently denied by tribal leaders. The workers' allegations are supported in a University of California at Los Angeles study in which researchers found that almost half the children of Rolling Hills workers surveyed were enrolled in state health-care programs for the poor.