Wait isn't very long right now. Two or three weeks depending on how many people come over and check in on the weekend that you come and how classes fill up. The people who checked in today have a two week wait. It is different for marines, though.
You can take leave when you get here if time permits. I doubt they will delay your classing up for taking leave, so if you can move in, send up a leave chit with 5 days notice, and return (if flying) NLT 2 days prior to starting, you should be good to go.