All these new ballroom-dance-related reality shows and feature films have us craving a smooth spot to glide across a dance floor. The place that comes to mind is a jazz club tucked quaintly into a corner of Uptown Plaza at Central Avenue and Camelback Road. Johnny's Uptown caters to those with aspiring twinkle toes. Its modest-size dance floor is set against a stage that's always bubbling with live music, one that allows just enough room to swivel and pivot yourself into a stupor. Dance soirees happen nightly and tend to run late, with such entertainment as Doc and Nayo or the Xcite Band playing until 2 a.m. Ella had it right when she sang, "It don't mean a thing if it ain't got that swing," and Johnny's is the place to swing it 'til it won't swing no more.