DEPARTMENT WILL IMPROVE AGENCIES' COOPERATION President Bush's proposal for a Department of Homeland Security with its own Cabinet secretary may be, as critics claim, timed to counter the impact of the congressional investigations into the failure of our nation's intelligence agencies to share information that could have provided warnings of the Sept. 11 attack.Nevertheless, and despite the turf battles that will undoubtedly ensue, the idea is a good one and the plan should be pursued. The agency the president is proposing would include the Coast Guard, Customs Service, Immigration and Naturalization Service and Border Patrol in its border and transportation...