I went into more detail on my experience last night over in
this thread, but I got in the park at 4:50, got in the pen right at 5, and was one of the first 30 people in the house when they opened it at 5:50. I really don't think you need to get there super early to get a good spot. Everyone just stands where the shade is lol. There are plenty of gaps to fill in up front.
As for the location, I want to say the entrance was by the Starbucks and Ben & Jerrys, but I could be mistaken. It's not hard to find at all though. It's barricaded so that you can only go certain directions anyhow.
EDIT: Found a picture to back up my memory. It is by the Starbucks: