Slongest: Ha! Guineas chasing cars sounds pretty funny. Our dogs aren't as big as a Great Pyrenees. We have two red Australian Cattle dogs who are about 60 pounds, and two little Jack Russel terriers. They'll chase anything out of the yard, but someone has to be home to watch them or they get in trouble. As for the bugs, we live on a small horse farm and so have always had trouble with flies. We used to get fly predators, little flightless wasps that kill fly larvae, but ever since we got the chickens and let them free range they've done a better job at keeping the fly population down. And thanks for letting me know you're selling guineas, but I live in Pennsylvania. That would be quite a trip for the little guys.
AmpersatChick: We don't have a problem with rodents, we have many barn cats and the two terriers who keep the mice population down. And the cats and terriers are afraid of the chickens (the hens peck at them if they get too close), so that's not a problem either. Our big dogs like to herd the chickens and protect them. We don't have a problem with opossums, bears, raccoons, coyotes, just those freakin' foxes. They're the only things brave enough to get close to all the animals we have here.
NicInNC: We live pretty much in the middle of nowhere, so unless they're really loud we shouldn't have a problem. We have a small flock (13 hens) so we'd probably get a few guineas. We've had problems with fleas before, and it's always good to get rid of mosquitoes, and I'm not sure the chickens go after those. Thanks for the tip!