Robstown Independent School District is asking taxpayers to vote on a referendum to refinance $9 million in existing M&O debt, a move officials say will save the district $3.4 million without raising property taxes.As early voting begins for the May joint uniform election, the district met with parents last week to explain the ballot measure. Robstown ISD referendum addressing school debt goes to votersRISD Superintendent Dr. Marc Puig emphasize…