I am a 7000+ hour, ex-RAF pilot, I fly commercially for a living and have done many many private hours in Florida, just for fun.
Mixture is wrong, around Daytona/Orlando/Kissimmee/Titusville, the airspace is indeed very busy. The instruction is equal to that in the UK, the aircraft are as good and the US have a positive attitude to aviation.
I have lived in the school 'houses' with people doing 3 week PPLs and can confirm this would be no holiday........ But it will be a fantastic life experience. 4-5 weeks would improve the experience somewhat, but 3 is JUST do-able.
Do your groundschool before you go, even if you don't do the exams, just trust me on this. Beware, the cost of the course usually stays the same if you do the groundschool or not. Also note that any previous flying you have done MAY be used by the school to reduce the number of hours you fly there. Once again, the course cost may go unchanged........ maybe say you have no experience......