when i worked there, i would tell people that as long as you get there before the opener, you should be fine with parking...any later and you will have to park in the neighborhoods, which angers the neighbors...but that all depends on
the show too - if its sold out, and its a big party crowd, people may show up later to chill on the lawn, and therefore, parking my fill up faster
to be safe tho, i would show up around 7:30..it'll take 10 minutes to haul yourself up that hill/wait for a golf cart to drive you up