Actually you are more likely to get assistantships in good universities, trust me. So instead of trying cheap universities, give a shot to better universities. Not necessarily Stanford, Harvard etc, but you can try the ones like Carnegie-Mellon, or State Universities like Penn State, Ohio State, Michigan State etc. You can also try Univ of Illinois Urbana-Champaign, which is known for its Computer Science program. I went to one of the above schools and all of my friends (all grad students) in Computer Science dept had graduate assistantships.