Tom,
We have traveled to FL in the winter for seven years. You will find FL to be more expensive than AZ. How much, depends on what you want
Northern FL (the Panhandle) is less expensive in the fall and the weather is usually good. The opposite is true in the spring. Prices go up considerably. In general, if you stay along the coast (Gulf or Atlantic) the costs are higher. If you are willing to go inland, they tend to be more reasonable throughout the winter.
Starting in Dec, if you want warm weather, you want to start moving south (below Tampa/Orlando). The weather in northern FL gets cold. If you are willing to put up with some cool days and stay north, prices are usually reasonable (less than $800/month.)
Starting in Jan, prices rise considerably in southern FL. This is their high season. Monthly rates can be in the high teens or more. If you decide to go farther south to the keys, be prepared to pay $2500 plus per month if you can find a place. I didn't mention the state parks because they fill up quickly during the season and are already booked by now.
Summarizing, if you stay in northern FL, you will find the prices aren't that much higher than Casa Grande. Fall and spring weather is pleasant, but the winter months are cold (some freezing days and nights), If you follow the sun to southern FL prices go up significantly.
Crystal River was mentioned in a previous post. This location is fairly reasonable in pricing and has mostly decent weather throughout the winter
A lot depends on what you want from FL. If you want the beaches and warm weather, you will pay a premium for it. If you just want warm weather and a tropical environment, go inland and the prices are less.
My wife and I are beach people and we have done both the Gulf and Atlantic sides. We much prefer the Gulf and are willing to pay the premium to be there.
Go to (rvparkreviews.com) and check out the parks in the areas that you want to visit and you will get a feel for what the parks charge at the times you would visit. From Pensacola to Key West, it is almost 900 miles, so there is a lot to explore.
My wife and I like to live by this saying when we are in FL
"May you always have a shell in your pocket and sand in your shoes"
Enjoy your travels,
Bill