Jeff
Several of us have spent time in the Keys in 'winter. Lake Effect is one of the boats who still owns their boat.
I sailed in the tropics for a number of trips--and on a sail boat we were comfortable most nights with a wind scoop letting the trades down the hatch. However, when coming to Florida, we considered AC an essential.
We always carry our AC if it looks like it will be hot at night. We do have several fan choices to push breeze down the fore hatch, and two fans in the V berth area. An "Endless Breeze" 12 volt fan is probably the best. We use several 5/8" dowel rods flattened where they hit the hatch rim to support the fan, external to the screens. We also use a Ryobi battery operated fan in the forward opening window.
As Bille says, during the day it is not an issue. At night if it is humid and does not cool off, then you need AC. That is going to be true of any boat--power or sail-=unless there is good Tradewinds. I have a Caracal Cat which is my bay and fishing boat. I have a large Bimini which folds flush with casting deck if down. The C Dory25 pilot house is more comfortable in hot weather than the Caracal Cat under the Bikini.
The running. If you are talking about true 3 to 5 foot short period seas--forget the C Dory--Even the Tom Cat, which I feel runs as well in a Contender or Regulator in 3' seas will not do it in 5' seas. 5' seas are pretty serious--and no boat I know of will be comfortable, except the larger cats, like a Freeman or the new Easterns in the 35 to 40 foot size. Also the large monohulls like Fountain, Yellowfin will be OK. I am very familiar with Panga, but you cannot run one fast into 3 to 5. They will drown you!

There are some similarities with the Imemsa Panga with its flat bottom. We ran out of Marathon in the Caracal Cat, and in many conditions it rides as well as the C Dory Tom Cat 255 because of greater tunnel clearance. But once much over 3 foot short chop--too much.
The key to the c Dory in any chop is to put the bow down with both trim tabs and a Permatrim on the motor. There will be spray, but you are in a pilot house and the windows can be closed (but if very hot--a catch 22). The other side of the coin--is that there are only a few boats with true cruising accommodations in this size. The Rosborough 246 is one which is semi displacement and will handle the chop better, but not 5 footers.... Lower cruising speed, and more HP, less economy. There are very few others such as the Ranger Tug outboard 23 and 27, and the Cutwater of same sizes. The World Cat and Glacier Bay cats don't have the accommodations. They don't run as well down wind/down seas as the C Dory line.
The other beauty of the C Dory is the trailer ability and being able to "Boater home" on the road. This is why many of the boats have an RV air conditioner or a window unit in the front opening window. We have it setup so that even us old and cripple folks can put the unit up in a couple of minutes. Run the Honda Generator if necessary, to cool the boat down--then in the middle of the night, the fan will keep you comfortable. (CO is always an issue, and we have 3 CO monitors in the boat--generator exhaust over the transom--and try to always have it going down wind from the cabin.
Get a ride in a C Dory and see if it will work for you.