I like Islamorada in the Keys, flat and shallow water. You can kite free at Anne's beach or kite for $10 at Seven sports right in the town.
There are few places there where you get equiment:
1st: Otherside boardshop http://www.othersideboardsports.com/
2nd: Seven Sports https://sites.google.com/a/sevensports
. ... s-company/