At Mayor Kevin Johnson's request, homeless campers have cleared out of a vacant lot used in a "safe ground" dispute with the city, he said Monday. Johnson visited the property near 13th and C streets, which is owned by attorney Mark Merin, over the weekend to discuss the ongoing controversy with campers, the mayor said in a late afternoon press conference. On Sunday, as many as 40 people left the property where they'd been camping for a month after saying they believe their statement has been made. They agreed to negotiate with the city for at least one legal campground, Johnson said. "I felt this would be a distraction if they continued to camp there illegally," he said outside City Ha