Last year, U.S. exports to Mexico totaled $163 billion, and imports from Mexico totaled $229.6 billion; nearly 80 percent of that trade crosses through land border ports on trucks and railcars; the 1.8-million strong Border Trade Alliance says bottlenecks at border crossings hamper this trade and make it more costly to grow it; the Alliance urges Congress and the Obama administration to invest in border ports of entry, including hiring more staff; Obama’s proposed 2011 budget includes only 300 new Customs and Border Protection officers, while Republicans propose shrinking the Border Patrol by 870 agents