TACOMA, Wash. — A Vancouver man was sentenced Friday to 13 months in prison for pretending to be mentally retarded in order to claim disability benefits. Pete J. Costello, 28, pleaded guilty in February to conspiracy to defraud the government and to Social Security fraud. He began receiving disability benefits when he was 8. He was ordered to repay the $59,226 he has received since turning 18. Costello, who cannot read or write, dictated a letter to his public defender that was submitted to the judge before sentencing and filed in court. "I know that it was wrong to 'act...