More than 1,000 volunteers will pick up litter in San Gabriel Canyon on May 30 in a program sponsored by the county and the Hughes Fullerton Employees Assn. Ecology Club, according to Supervisor Pete Schabarum. The cleanup, called Super Sweep 1987, will start at 7:30 a.m. at the Rincon Fire Station on Highway 39, about nine miles north of Azusa. The effort will continue until 1 p.m. Participants will receive free T-shirts and refreshments.