You can't really rely on Guineas to do anything you want them to do, lol. They may fly out, but then just pace back and forth squawking to get back in. Guineas are notorious for getting stuck behind a fence that they just flew over 5 minutes ago... they instantly go stupid and in their mind the fence suddenly grew to 50 feet tall and they will run themselves to death, pacing back and forth and working themselves into a full blown bird panic attack until either you rescue them or a predator nabs them. Sometimes having a landing board for them to jump up on helps with the flying in/flying out (but I personally shy away from teaching my Guineas that it is ok to fly over any fence in the first place, they stay closer to home and are safe from ground predators within my fenced 10 acres). And more often than not if given the choice to come and go as they please Guineas will choose the trees to roost in instead of the coop. Plus if the Guineas can come and go as they please... so can predators.