It's not good for workers PERIOD.
It works the same as NAFTA was alleged to have worked: increasing jobs in Central America while not losing jobs in North Am. On the surface, sounds like a worhty cause.
Unfortanately, it's been tried before. Most recently NAFTA, but beforehand all over the world, in the guise of the WTO/IMB, NAFTA, Chile and the Chicago Boys ... what's happening is a neo-conservative movement for something obstenably referred to as "free trade," but actually results in the loss of domestic jobs and the gain of short-term, exploitive jobs in the third world (jobs which in turn enrich already-wealthy American businessmen and stockholders in a trickle down system which fail to relieve the burden on the middle and lower classes).
Those are mt personal problems with CAFTA; there're a lot more reasons and links if you google "CAFTA."
http://www.stopcafta.org/