The driver of a bus that went out of control in downtown San Francisco at rush hour, killing three and injuring 15, has been placed on probation after pleading guilty to three counts of vehicular manslaughter. Salvadore S. Orogo was sentenced by San Francisco Municipal Judge J. Dominique Olcomendey, who rejected a prosecutor’s recommendation of a jail term. Orogo told authorities that the accelerator pedal on the San Mateo County Transit District bus stuck as he was pulling out of a terminal in the Financial District Jan. 19. The bus plowed through two crosswalks jammed with pedestrians. The prosecutor, however, said an investigation showed there had been no mechanical failure. The judge also ordered Orogo to perform 1,000 hours of community service and pay restitution to the victims. He also suspended Orogo’s driver’s license for three years.