I think I usually get in around 6 or 6:30, but I'm kinda crazy. Seriously the place does fill up quick and early though, so the earlier the better. As far as how to get back there, after you take the exit off hwy 44 and enter the convention center you can either go left or right and follow the road all the way around. Going left will get you back there faster though. I posted a picture with highlighted routes. The green is the shorter route (as you can see).