I have played every morning for the last 2 months at Sunshine RV Resort on Ohio Key and am told there is a group on Big Pine Key as well. The courts in Key West at Higg's beach are great and there is a pro there for lessons as well.
We have played in Key Largo during the winter months with some great people at the YMCA park. Try the courts at the corner of Laguna Ave and Caribbean Dr about 9 AM. Or go by there and look for a sign on the court gate with pickleball times. This is NOT the tennis court area, it's nearby. Wonderful group of players.