October is GMC Truck Month. There has never been a better time to buy your dream truck! GM has had strong incentives on 2010 models for the past few months, but with shrinking 2010 inventory, incentives for the 2011 model year have been stepped up. The 2011 Buick Enclave and GMC Acadia have upped their rebate to $2,000. There is good news for GMC Sierra truck buyers! The 2011 Sierras have rebates as high…