CAI stands for comando de accion imediata, but that won't mean anything to readers if you translate literally. They are actually tiny police kiosks around the city, usually just one room buildings standing in parks and plazas. I saw this rendition in the Guardian coverage of the protests the last two nights. If you haven't been reading and sharing news about the protests, please do. An international response could help. See my twitter feed @spaceforpeace for more.
My favorite response to the CAI burning was this: