Hi. Welcome to DR1.
Why? Florida already has a large Spanish Speaking community (you wouldn't have to learn Spanish to be able to buy a bag of nails), a long coastline with lots of beaches, weather that is similar to the DR, better consumer goods at cheaper prices. Florida is not a poor state that can't keep the electricity on, the tap water in Florida flows all the time (you can drink the tap water in Fla., not here), cars are cheaper there, the real estate market is stable, and it is possible to sell a property fairly quickly unlike in the DR.
If you lived in North Dakota, I could understand the attraction of a Caribbean island but not if I already lived next to the sea. If you absolutely have to live on an island, I hear any one of the Keys might be an option.
Without achieving a major change in scenery, weather and lifestyle, it's kind of hard to embrace your plan. You can duplicate your comfortable North American lifestyle here - it will be more expensive to do so than staying where you are. If you can live with rattan furniture, hit and miss utilities, and limited product selection outside of the two large cities you could consider life here a slight step down from where you are and if that's ok, hey you can do whatever you want.
Paradise exists on postcards and in books. Being a tourist here is not the same as having to slog through the daily grind that is 24/7 life in the DR. For someone like me where six months of winter can be used to offset the negatives of life in a poor, corrupt 3rd world country, I can justify living here most of time. If I already lived in Florida when I retired, I never would have moved to the DR. I would have chosen to move closer to the ocean or to one of the Keys or perhaps somewhere that (by outward appearances) isn't just like where I already lived - Think the foothills of Rocky Mountains for example- even if that meant shoveling snow or maybe New Mexico if snow was a deal breaker which it probably would be for my wife.
Good luck and remember, it's all up to you. No matter what anyone says here, you're going to do what you want anyways. Come spend 6 - 8 months here, seeing just how poor and ram-shacked it can be here, suffering through limited retail opportunities - I'd kill for a Lowes or a Home Depot, McDonald's or even fast food delivery on the North Coast where I have chosen to plop myself near where you are considering.
You need to come up with a few good reasons for living here, other than "it sounds like fun". The fun wears off really quickly when a power spike or a colony of ants fries your high-end TV and your steak never tastes quite like what you are used to.
On the other hand, I hear masochists love the Dominican culture, food, corruption, noise, pollution and official political conundrums - James might like that too.