It can vary but generally they'll let you in 15-20 minutes before your ADR, so that's about 8:45 or 8:50 (basically during the MK welcome show). Personally, I'd try to score an earlier ADR (at like 8:15 or so), so that way you can still take advantage of the lower early morning crowds. Otherwise, I'd push it back to 10:15 or so, so you can take advantage of the crowds then eat. Just a suggestion. Good luck!