Huh, I'm not a Californian by any means, but now that I think about it I say "the 217", "the 26", etc. Have I been corrupted by Californians that have moved to Oregon?
Right: "I drove out 26 to John Day to fill my elk tag".
Wrong: "I drove down the 5 to that new Sushi-Yoga place".
Here's an article that purports to explain why:
https://www.kcet.org/shows/lost-la/the-5-the-101-the-405-why...
And yes, it's definitely a Southern California/LA thing.
i would have said "the freeway through Cahuenga Pass."