If you are in S. Cal., why not grow any of a number of sub-/tropical clumping species? (I am sure some runners are more aggressive than others, so too none will ever be as potentially, aggressively spreading for you in your climate as compared to in the East with its humid, WET summers.) Runners are popular in many areas of the country because they can grow relatively fast and will tolerate very cold winters. Clumping Fargesias will succeed where winters are not too severe (or summers too hot), but not sure if any of these reach your height specification of 25 feet. I would investigate Bambusa, Fargesia, Borinda, and other clumpers. Also, are you under water restrictions of any kind? Bamboo are water lovers big time, especially while getting established.

Thanks for the suggestions! The primary issue with using clumpers for our given space is that it is extremely narrow, about 2 feet. I talked to the bamboo nursery, and two gardeners who work with bamboo, and all felt that runners would be better for the space since a clumper would end up damaging the surrounding patio space and retaining wall. All said the runners, although invasive, can be managed with the barrier and pruning. And they said the growth of the clumper mass wouldn't be as manageable. I'm not sure. I went into this thinking I would be looking at clumpers, and didn't expect to be looking at the runners.

After some more research, I have crossed S. Fastuosa off the list. There were too many accounts of rhizomes traveling fairly deep.

And Phyllostachys Vivax Aureocaulis is also crossed off the list. It's too big for the space.

So, I'm left with Spectabilis. People say the rhizomes tend to stay shallow, so it'll be easier to manage. And it does away with worries about it going under the barrier.

Another option is Japonica, which is also said to have shallow rhizome spread, but it's not as appealing to me as Spectabilis.

Just need to make the final decision if I'm going to go ahead with the bamboo or take the easy way out and go with Dodonaea Purpurea, which won't give me the height I want for the hedge, but won't have the same invasiveness concerns.

The bamboo is for a border that totals 85' by 2'. Given that the yard is mostly concrete, I'm not too worried about my water usage being excessive. For the past year, I haven't been using any water back there, since the border is just filled with dirt.