MIAMI — U.S. Border Patrol agents apprehended three Cuban men who arrived in the Florida Keys Friday morning. The men were found on the shores of Plantation Key in the Upper Keys around 8:45 a.m., said Adam Hoffner, division chief for U.S. Customs and Border Protection’s Miami operations. It wasn’t immediately clear in what type of vessel they were in. Hoffner said they told agents they came in a rustic boat, usually meaning a homemade, often barely-seaworthy, craft. Agents have not found a boat so far. “Agents are searching the area to locate the vessel,” Hoffner said in an email to the Miami…