As you've probably gleaned from the prior posts location has a big influence on price.
Panhandle sites will rent for little more per month than they would for a week in the summer as it gets cold that far north. Go to your favorite weather site and look up the climate charts for any given city/area and you'll see what I mean. While low to mid 60's will be the "average" highs in January, as example, they call them averages for a reason. You'll have some beautiful days in the mid to upper 70's offset by windy days where it won't get out of the 40's. During one of our February vacation trips to the panhandle some years ago the water fountain in the site next to us froze.
For those looking to enjoy shorts and T-shirt weather most days we generally recommend you look for something roughly south of the I4 corridor. Depending on the level of development and amenities you're looking for you can find nice parks in central Florida for $500 to $1000. The last few years sites in what is now our "home" park, while in Florida (Deer Creek
, about 20 miles south of Orlando), have been renting for $600 to $800 per month, depending on where in the park the site is located and whether or not it is inclusive of utilities or not. The grandkids will love visiting you here as you're no more than 20 minutes from any of the Disney parks.
As for making reservations, make them sooner rather than later. I've spent the last three winters in Florida and have noticed available sites are becoming more and more scarce, especially after the 1st of the year. I know the man we rented from those years has most of his sites rented for this next winter already when in years past you could have rented one of his sites with little or no prior notice.
Lastly, welcome to the flock (snow birds).