I believe Amdro Fire Ant Bait is the gold standard around here. Doesn't kill 'em by tomorrow but eventually poisons the whole colony.
http://www.amdro.com/Product-ChooserDrought has done a number on 'em around here too, that and crazy ants.
Birdwatcher
When I moved back to North Fl, the property we bought was over run with fire ant. Amdro killed them. Took a year, but they have not come back.