Covering the brugmansia should be just fine... We had down to 32º this winter and I just put mine under the eaves and they are blooming at this moment.
I don't know about the rest, but you could try christmas lights... I have heard those work well to keep stuff warm.
It is just so hard for me to imagine that I have warmer winters than Florida! :o) I am in Sacramento!

Hi
the big danger is frost rather than temps.That's why covering works. Be sure not to use plastic as it conduct heat away from the plant where it touches. Using a string of Christmas lights will help.Not the little ones as they only produce negligible heat. Also don't let them contact leaves as they can burn.
They make a special cloth called frost cloth but I find bed sheets are just as good. My really tenders are brought into the house. This is when I usually say "You have way too many plants." lol. Also I start again with "Time to build that year around greenhouse" But I can't figure out what to cover it with. lol
gary

The agricultural grade frost cloth works great. Its estimated to raise the temp 5 degrees, which can make the difference between 25 and 30 or 32 and 37, and it blocks frost from settling on the plants. It can breathe, and it can get wet without freezing to the plant. I have used it with great results for years. Bedsheets will freeze to the plants IF they get wet (personal experience) and bare plastic will freeze-damage where it touches a plant (personal experience) but covering a plant with a sheet or blanket THEN a layer of 4 or 6 mil poly film works better than either one alone.