My guineas (males and females) are coming up on 4 months old, and appear nearly full grown. I bought them a beautiful shed with two windows, and installed 2x4 perches. About the only time spent in the coop was night time. From dusk to dawn they are out roaming over several acres, decimating the tick popuation, and we haven't seen a scorpion in months.
Near sundown all I had to do was hang an LED lantern inside (guineas WILL NOT enter a dark coop) and the flock would rush in to get on their perches (albeit with an enormous amount of what sounds like angry screaming).
I had read in a few different forums that at around puberty(?), guineas go through a drastic personality change. The only change I've noticed so far is that the guineas now absolutely REFUSE to sleep in the coop, preferring instead a specific tree behind the house. And that they are now becoming more aggressive. A small dog lives a half mile down the road. The guineas one day decided to expand their horizons, and headed farther down the road. The little dog spotted them and went after them, barking furiously. The guineas took offense and went after the dog who, outnumbered 25 to 1, tucked tail and ran for home as if he had a pack of velociraptors after him.
We have a pitbull and four cats, and the guineas pretty much ignore them.
They seem to at least tolerate us, and if I make them scrambled eggs, it is a mad rush as they eat from my hand. However, they will NOT allow you to touch them, the way that chickens will.
When anyone unknown shows up, they will surround the person, and keep him surrounded as he moves from vehicle to house, doing that angry screaming sound (but as yet have not attacked anyone).
We moved here a year ago for the peace and quiet. The ticks were unbelievably bad, and we were finding a few scorpions in the house, so we kinda had no choice but to get the guineas, but the noise they constantly make is nearly unbearable. And if we want to enjoy some peace and quiet outside, we are soon surrounded by lots of yelling, squawking company.
Since they no longer will use the coop, I plan to order layer-chicks for the spring. It is my understanding that guineas can be extremely vicious to chickens UNLESS they were raised together from chicks. Even then, I've heard that the male guineas will sometimes try to kill your roosters. I will not be free-ranging my chickens.
One definite plus I have noticed is that the guinea poop is like little turds, rather than the liquid splatter of chickens.
The guineas are rather comical at times, and except for that ugly, naked white head, pretty birds. If you have close neighbors, my advice is do not get them. And do lots of research and watch YouTube videos. Good luck