The mayor of San Benito has entered a plea of not guilty to charges surrounding efforts to conceal a snow cone stand operating on his business property.  Mayor Joe Hernandez is charged in an indictment with abuse of office and evidence tampering.  Prosecutors say he proposed an ordinance revision he would benefit from, and took part in the city commission discussions on the proposal -- a violation of conflict of interest standards.  Hernandez is also alleged to have tried to keep the city from finding out about the raspa stand, which would have operated adjacent to his barbershop.