When I was in school UCSD had about 10 IFC and 8 NPC. There was also 2 Asian fraternities and 2 Asian soroities. Now there's a third Asian fraternity, one Hispanic fraternity and I believe 2 Latina sororities.
Eventhough it's fairly even, lots of sororities have socials with sports teams (Waterpolo=Yummy!) and fraternities at other colleges in town.
Josh,
Which school has more sororities? Is it USD? Ya'll can always do socials with them.
Also, if there not enough sororities you can always do 3 and 4 ways with other chapters that your friendly with.