Is it legal for a repossession agent to tell the borrower's neighbors that they are there to repossess the vehicle?

According to the Fair Debt Collection Practices Act, no this is not legal. According to this act, the debt collector must contact you only, or if you are represented by an attorney, they may contact the attorney. The only time a collector may contact any other person, is to find out where you live, your phone #, and where you work. Maybe think about filing a complaint with the Federal Trade commission. Their email is www.ftv.gov