If regular opening is 9:00, early entry will be 8:00. Depending on crowds they may open as early as 7:30. Usually it is closer to 7:45 / 7:50. Even if you aren't a resort guest, you can enter the front part of the park during early entry. At least that's what I have always experienced in the past. They will block you from going past the first part of the park to the actual rides, but you can get to the lockers, strollers, bathroom, maps, gift shops, bakeries, and restaurants that are at the front. This is great because it gives you extra time to get all settled and ready to go. You can enjoy a relaxed breakfast or cup of coffee or browse shops without wasting ride time later on. And you'll be one of the first non resort guests to get to the rides as everybody else arriving at 8:45 / 9:00 will still need to take care of lockers and stuff. They may even drop the non-resort rope early anywhere from 8:30 on, depending on how much earlier they opened for the resort guests.
So if...
Park opens 9:00
Non-resort guest
You are interested in having a relaxing breakfast, window shopping, or have lots of stuff to take care of when you first arrive, I suggest getting to the gate by 8:00 or before. The gates will open sometime between 7:30. - 8:00.
If you just want to go straight to the rides, I'd get there by 8:30. Inner ropes keeping non-resort guests out will drop sometime between 8:30 - 9:00.
Give yourself 15-20 for parking, security, and walking to the gate from the garage.
Plan on 5-10 minutes to get through the park gate if it crowded. Otherwise, you can usually walk right in.