PHOENIX (AP) - The Minuteman Project - an effort by citizens who have volunteered to patrol the Mexican border for illegal crossers and smugglers - has already borne fruit even before its official launch. Participants helped federal agents make 18 arrests near Naco, authorities said Sunday. The volunteers were surveying the border to familiarize themselves with the area before starting their regular, monthlong patrols Monday. "You observe them, report them and get out of the way," said Mike McGarry, a spokesman for the project that will concentrate on 23 miles of the San Pedro Valley. McGarry said about 200 people would be in place for Monday's patrols, although human rights activists and some authorities have questioned whether the project will attract as many volunteers as organizers expect. Law enforcement officials said the volunteers were keeping the peace, despite concerns they might become confrontational with immigrants. Many of the volunteers were recruited over the Internet and some plan to be armed. "Everything seems to be going well," said Carol Capas, a spokeswoman for the Cochise County Sheriff's Office. The Arizona-Mexico border is considered the most vulnerable stretch of the 2,000-mile southern border. Of the 1.1 million illegal immigrants caught by the Border Patrol last year, 51 percent crossed into the country at the Arizona border. In addition to the 18 arrests, volunteers reported another illegal immigrant after he wandered onto the campus of a Bible college near the community of Palominas, where about 100 Minuteman participants were staying. The man walked in and said he needed food and water. Volunteers helped him and notified federal agents, who picked him up, McGarry said. The man was weary from traveling but did not need medical attention, Border Patrol spokesman Andy Adame said.