Residents will have their say tonight on a measure that would scale back Montgomery County’s tax on carryout bags just a year after it was imposed. As of noon, 21 people had registered to speak at the public hearing, scheduled for 7:30 p.m. The council’s daily mail box has also been receiving a steady stream of comments about the proposed change, with at least 18 letters and emails received on the subject today alone, according to logs in the Office of Legislative Information Services.