WARREN — Home sales in Trumbull County dropped in June, while those in Mahoning County registered an increase, according to numbers released Wednesday by the Warren Area Board of Realtors. Though Trumbull numbers were down, there is reason for optimism, says WABOR President Andrea L. Lupton. Prices continue to stabilize and, in some cases, increase over previous months, she said. Low interest rates, coupled with growth at General Motors Corp. Lordstown Complex and RMI, continue to bolster confidence in the area’s housing sector, Lupton added. ‘‘The incentive package that the Cafaro Co. is offering GM workers ... should be a starting point for the Valley,’’ Lupton said. According to WABOR, there were 159 sales in Trumbull County in June, down from May’s 173 pace and well below June 2007’s 196 sales. Pending sales in Trumbull County stand at 217. Average time on the market increased from May’s 118 days to 130 days last month.