It's quite believable, generally, that they would be aware of it. I clearly remember hearing it the prior spring, if not earlier. I don't know how many people bought the record, but it was definitely a topic of conversation. Knowing all the words, and being able to keep up in real time is tougher. It was the first hip hop most people had ever heard. The general impression was that it was almost unbelievably fast and complicated.
I can buy one guy learning it, as an impressive stunt. Keep in the mind that there (obviously) was no Internet where you could find the words written out. You would've had to get the record and listen to it a couple of hundred times. Everyone in the car seems unlikely. Jumping for "Hotel, Motel, Holiday Inn," (or maybe "the Knicks play basketball") is about all anybody I knew could muster.
The "jock" part is pretty much irrelevant, I think.