You have a pretty view of the fruitless pear next door.
These are just my preferences, but I thought you'd like some opinions.

Ligustrum gets too big for my tastes, and it grows too upright.

Carolina Cherry is amazingly messy. Flowers are followed by fruits with nuts in abundance.

I like texas privets. I'll take some photos of mine for you this week and post them here.

I have had no problems with bees on my privets. The flowers are pretty but last just a short period of time. They are not messy, but in some climates they can go to seed. My yard is too dry for that to be a problem.

There are a number of other options, such as Springtime Viburnum, Arborvitae, and even rhaphiolepis. All of those will do well in your conditions.

Nothing will bother the privets, but ivy will grow up into any shrub you grow on that slope. If you have 37 shrubs, you will have to prune the ivy off from underneath each one to keep it from growing up and smothering the shrub.

I would plant Iceberg roses and privets together, with the privets a bit farther back and the roses just a bit in front in groups of three. I would also cut back the ivy to keep it out of the shrubs, and put in a metal or plastic barrier. Alternatively, I would consider planting Boston Ivy on the wall.

How long is the wall? That will give people a better understanding of how many plants it will take to screen it.

Good luck.

For me, I think avocados and citrus make fabulous evergreen privacy screening. Especially citrus can be trained where you want them. Very productive and pretty much take care of themselves. Not the fastest growing, but long-term I couldn't imagine much better.

Whatever you do, don't plant the trumpet vine! Very invasive!

I just saw a post on the Landscape Design forum, where someone was considering Sour Orange. They had a photo of it, and it looked amazingly beautiful! The trunks were all pruned up about a foot, and they looked really neat and pretty. Not sure how that hedge would do in Los Angeles, but the poster was in Phoenix.

Phoenix just had snow, so the climates might be similar. Of course that was unusual. Snow in Phoenix? :-)

Also, you would have to keep control of that ivy, because it will climb and co-mingle with whatever you put there.

Check out the Sour Orange! I read up on it. The fruit is bitter and pithy, but there are no thorns and it has small leaves.

Suzi

@hosenemesis - Thanks for the great ideas. BTW the one landscaper told he meant "Podocarpus" as he said Privet Wax Leaf and Ligustrum is the same (?). The reason, however, that he is pushing the Texas Privet is that he said it's the hardiest of the 3.

I didn't think of the fact that the ivy would grow into the shrubs and yes, it would make a mess. The barrier makes perfect sense but I imagine it won't be cheap to dig up that ivy, cut it back, and then make sure the roots are really gone otherwise if it starts coming back once the hedges are planted, ugh.

I'd get rid of the ivy but I think we have it and neighbors too as it helps with the erosion of the sloped portion of the backyard edge.

@yukkuri - My wife would love citrus and avacado trees but do they really grow together enough to provide privacy? And won't they get wide enough to take up a ton of room along that wall (the wall is probably about 100 feet or more)?

I suppose those types of trees would at least live better with the ivy.

@desertdance - Thanks for the Sour Orange suggestion. I'll take a look at it and ask someone at a local nursery.

And I thought this part of home ownership would be the stress-free part. Now I'm almost frozen trying to figure out what to do as it seems there is strong potential for regret or a do-over due to so much I simply don't know...and you hope the landscaper suggest what is sustainable and not just to make $$$.

Especially the fact that neither of the two quotes said anything of keeping the ivy away from mingling with the shrubs which makes sense that it would happen...and be a headache.

If they have sun, citrus and avocado create dense evergreen canopies, which are the best privacy on the north side of my property.

Citrus is very easy to train and shape to a fence or trellis.

I am less sure about avocado. I makes a big wall of leaves where it is, but not as good for training. I have trained a couple of branches on my big haas horizontally along the fence, but the thing wants to grow towards the sun, which is up and away from the fence...

The only limitations I can think of with citrus as a privacy screen are:
1) cost of putting in plants
2) somewhat slow-growing relative to common screening plants
3) won't do well if they are shaded
4) you are gonna need more friends to eat all the citrus

I'm short of cash for buying trees, but my plan is to grow a bunch of citrus from seeds and graft my existing citrus varieties onto the rootstocks all along the north side to fill current gaps.

If I had $250 bucks to spare I would buy 10 small citrus at the local big box (oxymoron) and put them in, no question.

I have seen some beautiful citrus tree espaliers, as well as citrus trained to cover an arbor. If you do a search for 'citrus espalier' or 'citrus arbor' you can see good examples.

A word of warning would be that dropped fruit can attract pests, with so many trees keeping all of the fruit cleaned up might turn into a hassle.

If it were my home I would probably use a lower maintenance plant for a screen, and have a few citrus trees in a different spot - a place where the fragrance can be enjoyed and the fruits easily picked.

I can't get a good shot of my privet hedge, since I need to go to my neighbor's to get it in the picture frame, but here is a photo of my privet tree. This is wax-leaf or Texas privet. A very nice plant.