Georgia Green

It sounds like guard dogs, llamas and donkeys should do the trick for long term, but If you're interested in a solution while you're still training them, I have a suggestion. I know someone who keeps a camera in her barn connected to her iPhone and some screens in the house so that she can keep an eye on her pregnant does, rather than sleeping out in the barn. This could help you keep an eye on your goats while your guard animals are getting into shape. I have one more tip in addition, though if you are a serious goat caretaker, which I assume you are, you should already know this, but one thing is that you should never leave your goats tied up. This leaves them extremely vulnerable to predators.

From my experience, you may have problems with the goats eating through the fencing. I've seen them work their way through even the toughest of fences. If you plan on this set up, you should probably keep an eye on them for a few weeks.

Keeping livestock takes commitment. If you are considering getting a cow or goat, you should prepare for what it might mean. Getting one of these animals is not simply a "making my own milk" kind of thing. It means committing to owning an animal. Besides this, as Wayne Fajkus pointed out, if you want milk, you need babies. That means besides that doe or cow you want, you're going to buy or rent a buck or bull to breed it with. You'll need to research and ask around to find a reputable herd to get a buck or cow from so that you won't get a buck who is unhealthy and will get your doe/cow and the babies sick. Now you have a buck/bull on your hands, possibly permanently. You also have to pay for the costs of breeding your goat or cow, such as a vet if you are inexperienced with birthing animals. Then after the birth, you have a young animal on your hands. For cows, generally there will only be one baby, but there could be a possibility of more. For goats, twins are most common, but triplets are not uncommon, and quadruplets are always possible. Will you sell them? Eat them? Keep them? For any possibility, you should consider your breeding options to fit your intentions.
Most likely if you want a good quantity of quality milk, you will start a herd, which takes a good deal of commitment. With that said, there is the dispute between goat or cow.

I myself am partial to goats. They are reasonably easy to care for, don't smell to much, easy to walk, don not require a great deal of space, and don't eat out of house and home. Cows are extremely smelly, large, leave a huge mess, not so easy to walk, and eat a good deal more than goats. They also need a larger place to roam.
That being said, cows do produce more than goats, and provide broader options no matter the kind if you do not wish to keep the babies. Goats are also needy. They need to be loved and cared for, and a larger herd is usually best so that they have company.
As far as quality milk goes, I would say that neither goats nor cows have better quality.

So as far as goat or cow goes, it depends what conditions suit you best. Just know that no matter what you choose, you must be prepared to work hard.

There are many goat diseases that can be harmful and possibly even deadly to goats, but none that I have heard of that can't be prevented by taking the right steps. The best thing to do is to find a reputable herd. Ask around like you were, see what other farmers think of some herds. See if there are any long-time farmers that can recommend a good herd. Good herds should be CAE, etc. tested and should provide proof that they are a clean, healthy herd. Steer clear of herds that can not provide proof, or are not clean and healthy. As long as you fid a reputable, healthy herd, renting a goat to breed with your animals should be fine.

Normally goats shouldn't have problems getting into crates. Although the younger they are, the easier. Some, especially wethers or bucks, are worse. What I would try is finding a goat that doesn't have a problem with going in the crate. The best candidate for this would probably be a doeling. A lot of goats will feel more comfortable doing things they would normally have to be forced to do if they see another goat who is chill about doing it.