John Leguizamo is a gifted chameleon with -- as he warned in the title of his debut solo 20 years ago -- his own special nonstop mambo mouth. He bounces off anecdotes and observations as a balloon careens around the room until the air is out, except that he never does seem to run out of air, or energy, or the ability to seduce an audience into the contradictory emotions that drive the public revelations of his life. What he does not have, alas, is an editor. "Ghetto Klown," the fifth chapter in what has become a live-onstage autobiography, runs almost 21/2 hours, including intermission. The length would not be an issue, except that his solo has compelling material for a 90-minute treat.