I don't see the appeal of Oleanders. They're ugly, poisonous and they require a lot of water.
Exactly the opposite . . .
Established Oleanders offer super sturdy year 'round green bushes upwards to 20 feet tall depending on variety with brilliant blooms and require minimum care and even less water. I have a row of Oleanders along the West facing wall of my home and they block the brutal afternoon sun and attract lots of lizards which in turn eliminates most of the insects.
Oleanders are also very common along the Southern California Freeways since they are able to block out of control vehicles as well as great for sound absorption.
Unfortunately, they are extremely toxic (primarily for certain animals), however, one would think anyone employed at a Zoo would be aware of that toxicity since it is relative common knowledge. I was more surprised there were no warning signs in and around the Oleanders, just in case.