To the OP: Muscovy can and will make some noise that is loud enough to be heard by close neighbors. They do quack, just not as often as other breeds. My 4 hens can get going with some chirps and other sounds and can be kind of loud. Even with clipped wings, muscovy can scale fences, especially if scared. If they are not legal, I would strongly urge you to have a backup plan in case you are "found out". Decide what you would do with them if animal control knocks on your door and says they need to go.
And yes, Kat Gold, releasing muscovy would be a very bad idea not to mention illegal. Believe me, I recently moved from Florida where muscovy are considered a feral species and because of that can be killed by anyone as long as it is not considered cruel. They also will breed with native ducks which result in infertile offspring. Therefore, they can decimate a native duck species.