Four of the five candidates for mayor of Los Angeles assembled in the Valley on Wednesday night and answered questions in a debate sponsored by the Sherman Oaks Homeowners Association. In responding to questions that were prepared by members of the association, Richard Alarcon, Robert Hertzberg, Bernard Parks and Antonio Villaraigosa addressed a variety of issues from city services, to big-box retail to ethics in government. Mayor James Hahn who is running for re-election, although invited, declined to attend the event. Although each of the candidates touted their own proposals on how they would improve services in the Valley and other parts of the city, many of their comments were reserved to attacking Hahn for not being at the debate and for showing what they said was a lack of leadership in his first term. The mayoral election is set for March 8.