These pictures looked familiar and even though I'm light years away from California, this might not be the plant you really want and for reasons other than for what it might or might not drop in your pool.

From "The Plant Press"
"Fallopia Baldschuanica is a rampant and potentially vast climber, useful if you have a few acres of wall to cover but is wildly unsuitable for small gardens. AKA "Russian vine", it has small green leaves and quite pretty frothy white flower plumes, on reddish stalks. It grows at the rate of a foot or so a day and intrudes itself everywhere. This climber must be used with care: it comes into its own in large scale landscaping - and has been used to great effect on some of the screening fencing round Heathrow Airport where it has colonized by the mile. It is one of those plants where you should stop and think before introducing it to the suburban patio!"

From MoBot:
"This is a somewhat weedy vine that spreads quickly by rhizomes. May be pruned back each year in late winter to 1-3Â from the ground. To keep within bounds, trim off excess growth as needed throughout the year.

Silver lace vine is a vigorous, adaptable, fast-growing, deciduous, twining vine that typically grows 25-35Â (12-15Â in one year)."

OK, I was kind of concerned about the rapid growth. What about Bower vine (Pandorea jasminoides) instead?

Really don't know, but information is readily available by searching under Pandorea Jasminoides.

Found this on "Floridata"
Pandorea likes a moist, fertile, well drained soil. This is a sprawling plant, and will need to be trained to a support and tied at first.
Light: Provide full sun or filtered sun. Pandorea does best in full sun, but still does well under high pines or in light, shifting shade. Roots by itself anywhere vine touches the ground.

If the Fallopia established successfully there it would be likely to get all over the tree, from which it shed numerous small flower parts in season.

2007 edition of Sunset WESTERN GARDEN BOOK lists

Beaumontia grandiflora
Bougainvillea
Fatshedera lizei
Lonicera hildebrandiana
Mandevilla
Monstera deliciosa
Solandra maxima
Tetrastigma voinieranum

as suitable vines for use near swimming pools. Since you are in southern California perhaps most of these might be possible there.

Any thought given to simply painting at least the cement portion of the wall? A better color blend between the brick retaining wall and the upper boards portion might make it recede into the background making covering it with plant material less problematic.