Here is a graph depicting the murder rates over time (2000-2012) in El Salvador, Honduras, and Guatemala.
It's good to see that each country saw its murder rate drop in 2012. Guatemala's rate has been trending downward since 2009 for a variety of reasons. Sure there have been improvements in the functioning of the police in El Salvador, but the drop is entirely due to the March gang truce. The drop of 1-1.5 points in Honduras - well, at least it didn't go up.