Clumping bamboo if you like a tropical look will be quickest growing. Clumping variety does not spread via runners, so it's not as invasive.

Some flowering vines could be another option...like bougainvillea or trumpet vine... but those will tend to require more trimming to keep narrow.

Grasses

Anything fast growing is able to do so because of extensive root systems. You may need to look at either buying full sized plant material, or planting in deep pots - or both. . Double potted trellises will allow you to have vines that don't get carried away and need trimming back as much...Don't know of any grasses that will get high enough to cover that wall, and most flop when wet.

The problem with clumping bamboo is that it drops leaves quite heavily, even thought hey remain fairly evergreen

see my link: www.romeocuomoceramics.com