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.

To jkom51: We are in the Central Valley where it is hot and dry. I'm not sure the sub-zone? I am concerned about shading the privet too much, as I still want to encourage them to grow up, up, up. Also, the soil is some clay/loam mixed with some amendments over the years. Not the worst I've experienced with pretty good drainage considering some clay in there. The line of plants are on drip irrigation. I don't mind litter from evergreens, as I think it can be charming in a well-planted neighborhood like ours. Plus, it's better than a ton of deciduous plants which would grow up to give a great block of the neighbor's ginormous Suburban guzzler, but then would leave it exposed once again come winter! Arrrrrrrrggghhhhh........ To "hosenemesis": Thanks for your nice compliment and suggestion. I have recently planted some escallonia in other parts of the front yard and was even considering filling in the ends with them. I've seen my neighbors mix up the plants in a hedge with success. I just don't know what to mix with privet. I'm unsure of the rules of how to mix plants in a bordering bed?? The nursery people suggested more privet but in shapes like cones or spheres, however, that gets pretty formal looking for my taste.

Pureguava, just to get the ideas started, how about the Arborvitae? I am not sure that 15' is possible, however. I have had a garden on distant property since 1996. Not long after I began there, a young couple moved in across the back fence. I can make a guess as when they planted the small Arborvitae. It would be sometime after Lowe's bought Eagle Hardware. The guy worked for both companies and they moved from the home about 10 years ago. So, sometime between '99 & '03 they planted Arborvitae. By 2010, with very little water and on the north side of that fence, those plants were a good 10' tall. In 2012, the current homeowner took most of them out. There are still 3 that must have been difficult for him to get to because he had a shed built near the fence with the Arborvitae between. They are probably struggling there but still look okay from my side, anyway. If you plant Arborvitae, be aware that they can be winter-damaged from snow. Tie them! Gee, the folks over there did a very poor job of caring for those quick growing shrubs! Steve Here is a link that might be useful: Evergreen Trees, Colorado State University