Euphorbias seem to make a nice hedge/screen. I have red euphorbias that are about 6-7' tall right now, and they have beautiful red foliage year-round, but they don't fill in super full. Maybe I'm just not pruning them harshly enough though. I have a neighbor who butchers hers every few months and they always come back like gangbusters!

I also have a hedge of Mexican pointsettia. I haven't been able to find out the official name of this plant. None of the pictures that come up on the web show what this plant is, but that is what it is called in all the nursuries I have seen it in here. It has small leaves, about 1 1/2" X 1/4", but it fills out nicely, better than the red euphorbia for a screen. In the winter (about November-February), the leaves all turn white, and it has a very delicate smell that is reminiscent of almond-flavored things. I have had my plants in the ground for about a year, and they are about 4' tall. I don't know if they are going to get much taller or not. If you look in the nurseries now, you could probably still find these with some of their white leaves.

We are about 1/4-1/3 mile away from the ocean, so we get a little salt spray but nothing extreme. I'm sure a good nursery would be able to tell you about the salt tolerance. Both plants seem pretty drought-resistant, and I haven't had any trouble with bugs on the red euphorbias. The Mexican poinsettias do attract whitefly, but it doesn't seem to cause any real problems. Happy gardening!

If you are on the ocean the best choices for hedge material is Carissa grandiflora called Natal Plum or Naupaka, Scaevola taccada. Another choice would be the dwarf Pink Oleander. Further back from the ocean you have more choices. Croton will take some salt spray and are colorful but are much slower growing. It always helps to check what the older properties near you have growing.

ilima

A lot of people near the ocean use Ironwood (Casuarina equisetifolia) as a hedge. It will grow into a tall tree if you let it, but I've often seen it pruned to about a 5-6' height. The fine needly texture makes it extremely wind and salt tolerant, and it also takes some drought. The roots are very competitive, though, and a lot of things don't like to grow near it.

Hau (Hibiscus tiliaceus) also does well in beachside conditions, and there is a variegated form with some reddish tones in the leaf, which is very attractive. Left to its own, it is a big sprawly thing, but it can be kept pruned down as low as a couple of feet high, or trained up on an arbor. The flowers are not super-attractive, but they add some interest. This is a nice plant that's been getting a lot of use lately-- Waikiki, Castle Hospital, among other places.

The idea of using the varigated hau is a good one. I saw it used in Kona very effectively. I have a photo if you can receive one.

I too moved from Northern CA 2 years ago. How about bananas or dwarf bananas? They grow very quickly and we have planted them in areas where the windbreak trees has broken in the wind! And you get a bonus with fruit! We live in Kaaawa, on Oahu, and we are about 300 feet from the ocean so the salt is harsh. We had 12 foot tall crotons as hedges, hibiscus, gardenias, tiares, Ti plants of varying colors, snowbushes do very well, and we also planted
bambusa vittata(Tiger bamboo or called golden bamboo here in hawaii)it isn't a runner, its a clumber and it grew to 15 feet the first year.
Good luck!!