Having lived in Fla. for many years on land and in boats in the keys, The humidity is a big deal. If you start with a hot rig and set your AC to pull to 72-75 odds are it will freeze up. If starting from high temp and high humidity take the temp down in steps of about 10 degrees at a time. When the unit cycles it will defrost then take it down another 10 ect. Odds are it will come down much faster. Over the years we found 80 to be a good temp as we could go out and still stand it. Lower temps kept us from enjoying being out.
One or two units is really up to you. But What ever you do be sure you get the cool air to where you want.. Fans or what ever needed. On our boats we had fans that never were shut off and the same in our airstream.. Our home had celing fans that were never shut off. Moving air helps.