We did 6 weeks in Florida in our 5th wheel last year for the first time. We didn't have any specific park in mind so we traveled around and stayed at 8 different parks, with one being a state park. We also visited several other parks. We enjoyed this adventure because it really gave us a better idea what kind of place(s) we might like in future snowbird trips.
Next winter we'll go for a longer time period reducing the number of parks and have already reserved a month at Rock Crusher Canyon in Crystal River. It's a bit north for real heat, but we're from Michigan and don't mind moderate temps.
We also plan to stay in the Sebring area for a few days as we did last winter. It's further south, but because it's away from the coasts the prices are less expensive. We stayed at Miami Everglades for a week last winter and wouldn't mind a longer stay, but a month is about $1,200, whereas Rock Crusher is about $650. While prices definitely vary you can expect to pay somewhere in between these amounts. Also, the shorter you stay the more you will usually pay.
Definitely do your research. You might want to do a week or two in different parks. That will give you a taste of the life in different parks. Good luck!
2018 Chevy 2500HD Duramax - 2015 Cedar Creek Silverback 29RE
16K Huskey EZ Roller Hitch - EU2000i Honda Generator