I have used bluf for preveting others from noticing you are casting spells. It only works if you try something plausible, not something like fireball.
Disguise works for impersonating some one or concealing your identity. There is a synergy bonus from bluff for convincing others you are a specific person.
Perform does not apply, that only means you are good at entertaining others.
Innuendo also doesn't apply, as you trying NOT to let anyone know you are casting, not sending some message to your buddy.
Slight of hand doesn't mean hiding specific actions, only taking objects or hiding small objects. Good to hide your material components/foci, not for hiding spells in general.
Of course, if they don't see you at all, it would be very hard for them to tell you casting spells. But you could not use Hide to prevent a person who is looking at you from noticing you casting a spell.
My advice: go around a convient corner. If there isn't a convient corner, well, you could always go evoker on them
