Tony, I sent a couple of your pics to Dave Ferguson who replied with this:
"The plant is Opuntia vaseyi. The name should be perhaps considered a nomen dubium, because the type locality was Yuma, Arizona, where no such plant grows, and it's unclear from the description and type specimen if this is the species really described (it could be, or it could be something from Arizona). Anyway, you'll also see it as O. magenta, O. austrocalifornica, and perhaps a few other names. All are often lumped under O. littoralis, but it's a very distinct and different species from that one. Yours is a bit spinier than average. Flowers are usually about the color of yours, but can also be magenta, pink, more orange, or even yellow. The fat ovary and later a usually very dark round fruit are typical.
Grows naturally basically in the Los Angeles basin (east limit is near San Bernardino), south I think near Lake Elsinore (maybe not quite that far), and north to the San Gabriel and San Bernardino Mountain base. Even though ignored and thought of as common, it is becoming a seriously endangered species in habitat."
Most recently it seems Opuntia vaseyi is thought of as a naturally occurring hybrid between Opuntia littoralis and Opuntia phaeacantha. (According to Baker and Parfitt).