Have you jumped on the mobile marketing bandwagon? A number of agencies recently have tapped into the trend. The city of El Dorado, Kan., and the Nashville, Tenn., Convention & Visitors Bureau now are communicating via Twitter, the social media network designed for use on mobile devices. In Dexter, Mo., citizens are receiving mobile text alerts from Dexter Parks and Recreation. The text alert program was established through a partnership with a local newspaper.