This is a long thread I just stumbled upon so I didn't do my due diligence and read through all the comments to see if my recommendation was already suggested so please forgive me if it was. I would plant 'American Pillar' Arborvitae along the entire fence line and give it a couple of years. It's cheap (I found them for $7.50 a pop for an order of 100 plants last year), narrow (3-foot at base when mature), tall (30-foot max), fast (3-foot per year, once established), densely evergreen (no see through branches), cold hardy (to zone 3), disease free and long lived (no known problems with a lifespan of it's ancestors measured in centuries). What more can one ask for? Here is a link that might be useful: American Pillar Arborvitae

Clumping bamboos (or runners if you're up to the challenge) might be perfect. The different species come in conveniently assorted sizes. It can be expensive to go for the clumping bamboo for so much length, but they really are pretty, especially the Fargesia species which are usually under 15 feet (you'd have to be sure to select one that's right for your climate). And of course for the lower screen, there's always the classic oleander...

I inherited an oleander hedge creating a privacy hedge for my front yard in Phoenix, AZ. Laughs at the sun. SUPERB privacy and acoustic barrier. I keep mine about six feet high, but can easily be grown to amazing thirty feet tall "walls" around here. I do get irrigation so I cannot speak to how often you must water it as I never do except for 18 irrigations a year, but the thick waxy coated leaves speak to a plant that conserves water. Pretty red, pink or white flowers or combine them alternating throughout your hedge. Few pests. Birds like to duck in and out of them. Downsides: Hard to get rid of if you change your mind. Need to be dug out 6 feet down. Whole plant poisonous. Generally don't eat it but since it tastes bad anyway not usually a problem. When cutting during maintenance the latex sap can irritate some people's skin. Occasionally, like once a year, I find a wasp's nest in them.

Hi I lived in Miami for 12 1/2 years and had a sister in St Petersburg.( she is gone) I was member of Florida Nuseryman and grower associatin ( Dade county)and have runed own nusery for short time. I forgot many collect spelling of plants and trees of Florida. After I check plant name spelling, I will post it. What is your garden size will be? . If you can post photo of your plot it will help and tell me direction, north south and shade or full sun. if shaded, moring sun ? or afternoon sun ? how many hours of sun ? or no sun at all?. How far from salt water ? within 2 miles ? or water front? Do you know how to use growth regulator ? ............ Some time people don't want to answer to questions and I understand it. More you provide informations , you get more usefull sugestions............ yama