I live in the North Florida climate as well, and share your frustrations with being "in between" zones. A portable hoophouse will work wonders for you to ensure your potted plants survive the winter, provided it locks out the moisture and wind.

The reason I suggest it be portable is because one year under the Florida Sun and your plastic will be yellowed, brittle and worthless. So some kind of structure that you can make based on your budget where you can take it down once things start warming up will save you a lot of expense of having to replace plastic every year. It's also far too hot in the summer, and anything inside would cook!

A more permanent solution would be a greenhouse, but you'd need heavy shade cloth during summer and high ventilation. I have mine under deciduous trees, that way during winter there's plenty of light, and in summer it's shaded, which helps but I still need to use shade cloth to make even staying in there bearable, so it's really not use-able in summer.

So there you have it - whether it's hoophouse or greenhouse will really be determined by your budget, but you'll get the results you want with either.

For more ideas on what might work for you, investigate the term "cold frame." Something as simple as putting the plants against the south or west wall and covering with a sheet can make a difference for some plants, especially if the wall is brick. You can also bury pots and cover the plants with a pile of leaves or styrofoam cooler. Unfortunately, it's really dependent on each type of plant, what might work best.

You may also want to investigate the FL gardening forum.

Hello Jax here southside 25 years. Got a little chill finally tonight. I know what you mean when you talk about being in between zones. I grow cacti and succulents outside. I have a rather large collection and they sit on staired shelves made with cinder blocks. When winter comes, and Tim Deagon will give you a 2 minute Doppler warning, I simply place my cactus down in between the cinder blocks removing the boards. I use a couple of boards to support 2 sheets of 4 mil plastic which i place over the blocks kind of igloo fashion. During the day the blocks heat up and give the plants a perfect place to live. Kinda of what a hoophouse would be. I do not remove the plastic till spring and everyone is happy. use whole sheets of plastic not strips and anchor down around the bottom to seal. I hope this makes sense.

In this video I show a small hoop house. I have chosen to cover mine with a blanket like material, but I've seen some that cover them with greenhouse plastic.

Here is a link that might be useful: My raised bed hoop house on youtube

you said you wanted to build it for under $200 and jason83 brought up having a green house, just thought I would let you know that I just got a small greenhouse 6X8 from harbor freight with a coupon for $199.99 , and some of their stores also sell the shade cloth for $25. I got the coupon in the sunday papers. Just thought I would let you know.

Another option is to just use frost covers on galvanized wire hoops. Frost cover could also be used to cover potted plants. El Paso, TX also has milder winters but probably gets a bit cooler than in Florida. Frost covers work quite well here even during the freezes.

Sharing some more information through the link to the article on this topic

http://www.elpasotwigs.com/garden/winter-protection.html

Here is a link that might be useful: El Paso Twigs