If the conclusions of the research that Steven Levitt explains in this video also apply to Latin America, then crime can be reduced easily. How?
Reducing the incentives to work for criminal organizations by providing information. Providing information can work extremely well to change social behavior as Esther Duflo explains in this video -- although in the case of education policy.
Members of gangs should know that the probability of being killed whey they work in a gang are much higher than being in a war zone, like being in Iraq, for example. Levitt says this probability is 25% in four years !!!
They also need to know that working for a gang will pay a very small salary, even lower than the salary they would get if they work at a McDonald's. They also need to know that the probability of becoming a gang leader, within the organization, and earning a higher wage, is very small. Working for a gang means being trapped in a low-wage / extremely high-risk job. Gang members, specially those at the low ranks of the organization, overestimate the gains and underestimate the costs, and they should know this. This message can be delivered on TV or Radio.
From a social sciences perspective it seems that a combination of sociology and neoclassical economics is a very powerful way to understand gang activity. I posted a book review on this regard previously.
I know that this means importing research results from a different context, but in the absence of local research, this might be reasonable, and there is not much to lose.