I live with two girls. If you're a reasonable, diplomatic guy and the girls are mentally stable, it should be cool...
I've had alot of fun with my roommates, lots of parties. you just have to forget about
A. decorating the house the way you like it
C. making a mess all over the place
D. being a proud chauvinist
other points and tips:
-decisions are easier with 3 people, 5 peeps can't agree on anything.
for example throwing parties with people who have the same school schedule is easier.
maintaining the fridge order, etc. it only takes one of the 5 ppl to slack off w/ dishes and eat everyones food and it's a living hell
-getting the whole rent paid in time is easier with 2 people
-more time to use the bathroom in the morning w/ 2 ppl
I also strongly suggest not getting too excited about having titties bouncing around the apartment. the fact they have boyfriends & that you seem to be not intrested in the girls in that sense, to me it sounds like a good thing and a matter of keeping the apartment peaceful/drama free.
everything depends on human personalities and who you get along with. If you already think you can't stand someone of the 5 peeps, i'd forget it if I was you.