I feel that "you guys" to refer to a collective group can be considered sexist depending on the receiver, but that the intention of the person saying it should be weighted more than the inherent nature of the choice of word.
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In all seriousness, if you're in a close enough group that will know you're being humorous, why not? I know I'd get a good laugh if someone came up and used that one on me.
I've had a friend wander in before and go, "Sup, ya fucks?", so it's not entirely unheard of.