It's not even the weekend, and the Miami Book Fair International has so far delivered a who's who of celebrated authors in Tom Wolfe, Junot Diaz, Sandra Cisneros and others. Literary giants though they are, consider them a palate cleanser to what really draws the glut of book lovers to downtown Miami: The weeklong fair's most-popular and best-recognized feature, the open-air sprawl of booksellers and music known as the Street Fair.