Mariachi music and folkloric dancing on Sunday replaced the country swing and fiddling music that has been the custom at the Colorado State Fair. On the day set aside to celebrate the Hispanic culture, the entertainment sites on the Fairgrounds were filled with Tex-Mex music, mariachi groups, the Charreada (Mexican rodeo) and folkloric dancers. "Fiesta Day is the only day I come to the Fair," said Robert Gomez of Colorado Springs as he watched Mariachi Arc