We've had guineas (started with keets) for three years, and we're still learning stuff about them.
1) Yes, but like Flgardengirl said, they do having a laying season unlike chickens. They normally lay from March to September, sometimes earlier sometimes later. If they don't have a nest and are coop trained, they will most likely lay randomly in the coop or run. Some people have gotten them to lay in the nest box and we've found a few guinea eggs there too. They do lay daily, when they have a nest.
2) Yes, guinea eggs are just as edible as chicken or duck eggs. I believe them to be healthier since guineas are out in the fields eating bugs, seeds, and greens moreso than like chickens. The shells are generally very hard.
3) I've never eaten one (Not yet anyway!) but yes they are. I've heard they taste more gamey than chickens. (Also, guinea hens are often used on Food Networks "Iron Chef America")
4)(I'm going to leave the pros and cons for the end, so this is the answer to the question about having more than one cock) Guinea cocks will generally take 1 or 2 hens as their mate(s), so supplying one cock for every hen is best. Like with chickens, the more dominant guinea cock will show the more submissive cock who is boss. If you have 5-8 cocks then you probably won't have a problem with picking. Sometimes though an older cock will pick and chase on a younger, more submissive cock. Make sure you don't overload on cocks (unless you don't want any hens, then they might act different) and you should be good.
5) Yes, guineas LOVE fields. They love eating grass seeds, grasses, bugs, ticks, you name it. They're not too much for forest but they love the fields. Some supplement feed is good to keep them in top shape (tip: Give them their feed at evening when you'd want to lock them up to help with their coop/run training)
6) Mine will come close to us, but prefer not to be touched or handled. They'll struggle when you catch them but eventually settle down a bit. Some people have had guineas that will hop on their laps though, so it all depends on how much time you spend with them when they're young.
7) I think this is the most asked question, hehe. Yes, for their first year they will be quite the little chatterboxes (Especially since you'll just be getting used to them) Bear with the buckwheating and alarm calls, and when they reach about a year old they'll pair off and quiet down a bit.
8) We're still working hard to figure out the way to get the best hatch from our guinea eggs. This year I kept the humidity at 60-70% during incubation (We don't have a wet bulb thermometer) and temperature is pretty much the same as chickens. 99.5-100 for incubators with fans and 101-102 for incubators without fans. On websites you'll read that they take 28 days to hatch, but mine normally pip by day 25. Keep the humidity as high as possible during hatch, because the shells are much harder than chicken eggs. Don't be alarmed if the keets (Proper name for baby guineas) take a day or a little more to hatch. If they look like they're getting dried out, wrap them in a wet, warm, paper towel.
Now pros and cons..
Pros: Eats bugs, extremely entertaining and funny to watch, very hardy once reaching maturity, generally good mothers, very intelligent when they want to be, will come when called or when they see sight of humans, oh the list goes on and on .
Cons: Some people do consider them noisy, they like to lay in the field (which is not exactly a con, its instinct) sometimes you might get a pretty mean cock (and then his best direction is probably the dinner table), and they like to roost in trees unless trained to a coop. In my opinion the pros out weigh the cons.
Now, as for this predator subject..We very rarely ever lose a free ranging guinea to a predator UNLESS it's a hen setting on her nest. Setting hens MUST be caged or protected with fencing. Critters love their eggs and something (We don't know what, yet) has carried off a nest of 24 eggs AND the hen once from our farm. To follow a guinea hen to her nest is not very hard, but you need to observe her and her cock closely. First find out if you really think she has a nest. Often hens won't lay unless they have a nest, so to figure this out keep them locked up for a day or two and see if you find any eggs around the coop or run. Most of the time after doing this, the hen will be eager to get back to her nest and check on things. So after you let her out, follow and watch her from a distance (not too far though, as they can quickly disappear into tall grasses and brush)
Another thing, guineas legs seem to be quite fragile. We often have a cock with a limp, but this goes away within a few days. I never ever catch my adult guineas by their legs as I do my chickens sometimes. Guineas legs have some strong kicking power, but they just seem to be able to pull muscles or hurt themselves in otherways easily. Other than that, guineas are durable little buggers after they become adults.
I really hope I haven't written to much . Sometimes I think I do but I just have so much that I want to share, and I'm so happy to see another person engaging in the world of guineas. Goodluck!