LEAD: ON MARCH 10, TWO REPRESENTATIVES FROM THE FEDERATION OF CUBAN WOMEN, SPENT THEIR LAST EVENING IN THE U.S. SPEAKING AND ANSWERING QUESTIONS AT AN EVENT, HELD AT THE MARTIN LUTHER KING AUDITORIUM IN MIDTOWN MANHATTAN, ENTITLED WOMEN AND THE CUBAN REVOLUTION TODAY â ADVANCES AND CHALLENGESÂ. WBAI FRED NGUYEN, ATTENDED THE EVENT AND PREPARED THIS REPORT: