trin, if you are just wanting some goats to clean up your weeds, get a couple of good feral cross boer does. They are tough as nails and will do a good job cleaning up the place. They are the hardest of goats to fence, but a hot wire close to the ground works well because they have a tendency to push under loose wire. Full feral animals can go over fences but we have found once they have a bit of boer blood they prefer to go under rather than over. Also, some animals will get over a fence by climbing up a diagonal stay.
On the other hand, if you are thinking about feeding out wethers, to really get the quality and quantity of meat you need good Boer or Kalahari animals. They also need good quality feed - a mixture of pasture and browse, grain optional. Fullblood boer animals will clean up the weeds and do well on them, but to produce to their full potential they need a balanced diet of both pasture, browse and minerals.
We feed out boer and boer cross wethers and turn off 25 about once a month at around 30 - 40 kg liveweight. They are aged around 6 - 8 months, some younger some older. There is good money in it (over here anyway) provided you establish a market.
Have you thought about getting a few angora wethers? You could get some fairly cheap at around 2 years of age, once their first valuable fleeces have been harvested. Here you could buy them for around $20 a head. The nice thing about angoras is that they are a lot easier on fences than the other breeds. Any fence that keeps a meat breed sheep in will also keep an angora in. If you get them off shears you will have about four months before the weeds will begin to contaminate their fleece, but if you are not concerned about this you can usually graze them on the weeds as long as you like. And if you like you can then put them in the freezer. Angoras may take a bit longer to reach slaughter size than the other breeds but the meat is just as good.
From our experience, goats are not a particularly sickly animal. The person who told you this may have gotten the idea from the fact that goat kids are fairly delicate when they are born, and susceptible to cold, predators and illnesses. But if managed properly, these aren't a problem.
And yes, they will crap everywhere and then they tend not to eat feed if they've crapped in it. But, the soiled food we feed to the cattle and pigs, they are really good at sorting through it.
Wow, sorry for the long post but hopefully it helped.