Welcome to S&R, you will find much help and support here. I am sorry about your son, he just seems to make the wrong decisions right now. I have an adult recovering ad who was doing coke. I believe she waa doing it for many years before I found out about it.
Your going off to Florida while he is in rehab, it will give you time to think about what your going to do.
Was he working at all when he was out of rehab? Does he live at home? Maybe being with the oldfriends he hung with didn't help.
Addiction is a terrible sickness and needs a lot of the right attention.
Come here and get lots of ideas for help for all of you and good luck to you all. Also Naranon meeting are wonderful to get support while you are in Florida and when you get back.