Latin America: A weekend march by 5,000 Bolivians in favor of a free trade pact with the U.S. got little attention. But it was a clear signal to step up commerce in a troubled region we often don't know what to do about. Bolivia is the poorest country in South America. The prospect of a growing free-trade movement, coming from humble factory workers, is startling. It surprised even other Bolivians who often hear anti-free trade rhetoric. After all, just about the only thing we ever hear about Bolivia is that a far-leftist, Evo Morales, leads in the presidential polls for...