Guineas mate for life. They bond as a flock-- much much more than do chickens-- and they have a flock intelligence that each bird depends on. I don't know what your situation is, or why you only want 3 birds, and I wouldn't want to suggest to anyone they keep more birds than they can manage, but after keeping them for a year I know I would not choose to break up their flock. They mourn their dead. I'm just glad we got them as partners on our farm for insect control and that I don't have to sweat trying to sell them or planning to eat them-- I've seen what happens when they lose members of the flock. If you are going to part with some, I would advise doing it when they are young keets and before they've made life bonds. That would also make it easier for the guineas who relocate (adult/older juveniles can be hard to persuade to stay where they are relocated). It took many months before we could tell the difference between the two sexes and even then the physical characteristics aren't solid, and it's hard to isolate each guinea to listen to their voice to tell. The last bird who got killed on the road was a female (eggs inside), but we would have pegged her as male just by her looks.
About road safety-- we have lost 4 birds to the road in the 6 months they've been free-ranging. Three were in one accident, and after that they stayed more out of the road, but recently there was another loss. They are trying to be savvy about the road but they stand there and discuss/argue about where the flock will go next and too often that puts them standing in the road. And if someone dies in the road they will stand there trying to get that bird to get up and come with them, for quite a long while, all the while being in more danger. It's not a great thing, the road.
You can't put boundaries on them-- they will go where they want to go. However, for a long time I would go out and shoo them out of the road, I did it at least once every day, figuring I was at least impressing on them that there might be a boundary. Don't know if it helped at all. We have neighbors across the road and up the road a bit, in both directions, and they all really enjoy the guineas, fortunately, because the guineas make their rounds everyday.
They walk most places because that's where they hunt for food, on the ground, that's where the action is. So yeah, most of the time they are walking or trotting across the road.
We're thinking about putting up a fence along road. Probably won't detour the very persistent but we're hoping it might help a little. We have plenty of room in every direction and even over the road is ours. Just worried about them getting over it. Just lost a Muscovy on it this week. We had too many males and one chased her out on it. So I'm worried about getting too many males and having a problem. What kind of ratio works for them? If it's not as big of a deal like other birds I'd probably keep more but I'm worried it'll be off and I'll have more problems...