They do like to dig some deep dust bath holes. They will nibble on plants, just mainly like the seeds, though. I guess if you could get them in and out of the garden when YOU want, that would be great. Mine, unfortunately, do what THEY please, and there's no way I could chase them down to clip wings or get them separated from their chickens. Would have helped to have bought them before they were adolescents. I just bought some super-soaker water guns and they are already pretty helpful at training the guineas to stop picking on the chickens, which they think they own. Also, pretty handy for rooster training. Don't get me wrong, I love my 2 guinea bully brothers, but they are the Eddie Haskells of the poultry yard. Don't believe everything you read about them. For instance, I picked a deer tick off my friend's shirt who was working in my yard, and as far as alerting to strange people, they only screech when they see me. They do perform well at herding the chickens against the house or trees when hawks are about. They are low maintenance, eating mainly what they forage, and living in trees. I've read they wouldn't last long in trees, but I really can't see anything messing with full-grown ones. I don't have females, as my couple turned out to be bros., and I hear they are even noisier.
I love guineas but they sure are noisy all right. Too bad they make such lousy mothers. I always hatched my guinea eggs under a hen. I had a old Rhode Island red I called "Auntie". She was ALWAYS broody. She'd adopt any chick if another hen turned her back for a second.