There was a similar question asked today from a guy that was in college. I want to start but.
I am in college and if you plan accordingly you should have no problem getting 15-45 minutes of alone time per day to do PE. Someone posted in the thread I linked how you can do some exercises with just a little privacy(a blanket or darkness. I am not all that shy with stuff like that. I would do PE movements and exercises on the top bunk in my dorm room with my roommate in the room(and I was the good roommate compared to him). ;)
To answer your question, from what I have seen, different things work for different people and some good gainers on this site find that they gain best when they split their routine.