Welcome to On the Radar, where we preview upcoming arts events to mark your calendars for. NYC, Detroit ... St. Pete? So our sweet hipster haven might not be on the national hip-hop map, but the bboys, DJs and graf artists at Saturday's Urban Elements are blazing their own path next Saturday. They're dropping the five founding elements of hip-hop (MCing, DJing, breaking, graffiti writing and knowledge) on Central Ave to commemorate its first legal graffiti wall.