Hope Ruben doesn't see your post because - as you can see from the title of his book - low rider music and culture in the US goes right back to the 50's. And it was very much an active and thriving music culture and "genre" (as you refer to it) by 1979 !
The irony is a number of tired, jaded old people in the UK (not referring to you Happy Feet!), who've become disillusioned with the northern scene, have now hijacked low rider music in the last decade and been paying ridiculous sums of money for records they would have literally chucked in the bin back in the 70's and 80's !