I'd be really surprised if security let people in at 3am because that would require extra security to deal with them. (Note: to get into Vista on check-in day, you have to show proof of being in the CP. So you are stopped at the gate and can be turned away.)
My dd got there early (about an hour before check-in was supposed to begin). She was close to the front of the line on that day. At her point in line, there were plenty of two-person apartments at Chatham available, but she wanted more people than that and chose Vista. She made out fine and feels the idea of Vista being some sort of pit and party place was vastly oversold. To be honest, we and the rest of her roommates' parents all thought Vista was way nicer than the dorm rooms at their colleges.