You can always check in whenever you arrive. Even if you arrive at 7:00 am. There is no guarantee you will get into your room that early though. If they had empty rooms the night before, you will likely get lucky, but if not, you will have to wait until your room is ready to take occupancy. Check in time is officially after 4:00, and sometimes they don't make it by then either.
We usually check in as soon as we arrive and then head to the parks and come back to the resort around 4:00 or at least call the number to see if our villa is ready.