WEST PALM BEACH — As commuters may recall, West Palm Beach Mayor Lois Frankel took advantage of a roadside sign along the North Dixie Highway reconstruction project to express empathy with traffic-bound drivers this month. "I Am Mad Too! - Lois," her message flashed. Now, someone has responded anonymously to the mayor's frustration. Tuesday morning, the electronic board displayed an obscene message. Whoever left the message then locked the metal box housing the sign's keyboard, so that road workers were unable to change the words and had to shut the sign off altogether, which they did shortly after 9 a.m....