Yes, you can get your IKO card at Crandon. Will cost you a bit though.
But you need it to ride there.
Make sure to checkin and get the do's and dont's of the spot, has some rules, but is a dream to kite. Go for sure!
Wind forecasts can change a lot in Miami...week before it looks excellent, and the it keeps postponing it the closer you get to that day...so a day before you really know if wind is coming.
If you drive along the North Beaches, for sure you will see kiters if there is wind. Pass by the beaches mentioned on splocs.com
Make sure to ask locals as well for do's and don'ts. Normally easy, but few spots need special attention, like Fort Lauderdale beaches.
In general, just don't ride inside the swimmer zone buoys and you will be fine.
You can also hit up the local kite shops to get more info and meet some people.
Have a great trip!