Entering Race, Ferrer Focuses On Giuliani
Borough Pres Fernando Ferrer of Bronx enters race for mayor, moving aggressively to separate himself from his Democratic rivals by declaring that he will be advocate for 'the other New York,' which he says has been neglected during eight years of Giuliani administration; this tack is notable in a year in which many polls show that voters believe New York City has been heading in right direction, even if many people have some questions about Mayor Giuliani himself; photo (M)