Depends. We always arrive early. Sometimes we have been seated early, sometimes we are seated within a few minutes of our ADRs times, and sometimes we have waited waaaaay past our ADR times. It seems like Ohana and Le Cellier are the two worst for running really behind. With an early time like 5:30pm though, I'd guess you have a good shot of being seated close to ontime. The longest we've ever waited past our ADR time was almost 75 minutes at Le Cellier one night. Oh yes, we also waited a really, really long time past our ADR at Rose & Crown and also Chef Mickey's before.
By the way, if you show up too early for your ADR, some restaurants will tell you to come back no more than 15 minues prior to your ADR time. I know we've arrived 30-45 minutes early and have been told to return closer to our ADR time at Le Cellier, Crystal Palace, Ohanas, and probably a few others.