Tough guys do dance. While on location in Memphis and Chicago filming the upcoming drama A Family Thing, Robert Duvall (Something to Talk About) made an odd request. ''I made sure they installed a dance floor in my hotel,'' he says. No, the 64-year-old Oscar winner isn't making a workout video. He's exercising his other passion: the tango. ''I practice about two hours a day,'' says Duvall, who works on his moves solo. ''I think you should approach your hobby with the same ferociousness you bring to your work.'' Did Duvall, who's working on a script about a tango dancer, get Family costar James Earl Jones to shake a leg? Jones says he's ''not much of a dancer,'' but Duvall won't be taking no for an answer. ''James and I have to talk. I wonder what he's doing later?''