I know Disneyland, Knott's, and SFMM pretty well. I can give you tips on when to ride what, best places to sit, best times to go to certain rides, etc. but I haven't memorized every food area or bathroom quite yet...
I probably know SFMM best out of three, because I've gone there the most recently, but I've really only been going to the park's "officially" for a few years...(I've always gone to KBF and DL, but I used to be scared of coasters and not really pay attention to where things were other than rides).
I dont think I've ever needed a park map at the parks. Even on my first visit to SFMM in 2006, when I didn't ride one ride, I knew where all the coasters were. I also don't think I needed a park map on my Midwestern Trip this year to CP, Kennywood, KI, Coney Island, SFKK and HW...had those parks memorized too.