Can your son add either a lattice panel or a fence-top pergola structure to allow the vines to grow higher? That would be a much better solution in the space allowed. Ficus benjamina would be a disaster, don't even think about it unless you plan to keep them in large pots -- in which case they won't be tall enough to screen effectively.

A large scale example can be viewed on the link.

Here is a link that might be useful: {{gwi:42447}}

The pittopsorum is a good choice - very fast growing and quite airy. It is used frequently in SoCal as a privacy screen.

I would not put too much stock in reports of sudden die off. I've never encountered it, except here in the PNW where the odd bad winter (like the one just past) will freeze it off. I've used it a number of times in designs in coastal Orange county and have not had a problem with it but it may take a little more attention in hotter, interior locations. And I'd question the allergic reaction to just touching the plant. It can raise some allergy concerns with pollen and it is toxic if ingested (and a great many other plants are as well.....that's why humans tend not to graze their gardens!), but according to the UCDavis toxic plants listing, it is NOT known to produce dermatological reactions.

Podocarpus is a common evergreen screening plant as well. Can be sheared and hedged at will but rather slow growing compared to the pitt. Clumping bamboo is another possibility. Any of the Fargesia species should rapidly achieve a good screening height.

I took "sudden death" to be a reference to Phytophthora ramorum.

I'm not sure of your zone, but we used a combination of leyland cypress and burford hollies to screen our neighbors. It is pretty because it is thin and feathery, with glossy leaves.
In another place, we used arizona cypress, they get big quick and are blue, very pretty. We put some leylands with that and some crepe myrtles. I think pretty.
{{gwi:42454}}From 264 Adams Place Drive

Oh - I didn't see your 2 foot limit... hmmm.... gardenias are nice, green and smell pretty? :)

I'd go with the hardscape suggestion already tendered. Permanent, attractive, and not subject to the vagaries of climate.

Here are your ficus benjamina -- with the buckled and rebuilt and buckled again brickword purposely omitted from the frame...

{{gwi:42455}}

These are examples of lattice topped fences:
(choose a vine less destructive than the algerian ivy seen here on the lattice)
{{gwi:42456}}

Plant collection to distract the eye ; )

{{gwi:42457}}

In this tight space the dining room window would look at a blank fence, were it not for this large fence-mounted trough of shade-loving plants:

{{gwi:42458}}

{{gwi:42459}}

One more planted out fence:
(I doubt these orchids are permanent, but they do dress up the woody vines)
{{gwi:42460}}