I have a lot of friends who are SJU fans and sometimes go to games with them, even where they aren't playing the Hall. They draw pretty well as long as they are decent, and obviously there is a uptick when they are good, like Lavin's first season or even last year. Remember their attendance numbers, on average, will never be as high as others because the on campus facility only holds about 5000 & change, and they play a lot of games there (most of the non-conference against smaller teams, plus several BE teams).
That said, as I stated on another thread, I was shocked at how well they drew on Sunday. Was my first MSG game this year for any team. No surprise the Cuse game was higher, as I watched on TV and I'm sure that place was at least half Cuse fans, if not more.