Congrats on your first trip to LA. Hope you like it!
Parking is a bit of a pain in the butt around the CC, unless you don't mind paying for parking on Figueroa (usually it's way too overpriced for my taste $20-50). However, this might be your best option since street parking on Saturdays is not quite practical, most of it is metered, with 1-2 hour restrictions. You'll find more inexpensive parking the farther away you go from the convention center on Figueroa or if you turn right on 9th (it's a bit of a walk). Keep in mind that LA live, which is adjacent to the CC, is a popular tourist destination, so parking is will be somewhat pricy on weekends regardless.
As far as nice roads, PCH to Malibu is pretty, but not terribly exciting. If you want something more fun, try Sunset Boulevard off of PCH on your way back from Malibu for a truly LA experience (especially if your hotel is close to Downtown, because it goes all the way back), or take a canyon road like Topanga or Mullholand (keep in mind that there are two sections to this particular road, so plan ahead or have a GPS handy).
If you have any specific questions, let me know.
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