As soon as I walk outside to the Boyle's Garden Tallboys across the fence try to attack me and I get killed by all of the guards.

Why is this happening?

Didn't have this problem, but maybe you alerted them on your way in? I can't think of much else that would cause this.

That was what I was thinking but you'd think that when you get into the party they will confuse you for a guest or at least not attack you when you're surrounded by guests.