I've got no answers that will make you happy.
In-floor cleaning systems are one of those ideas that sounds good in theory, but are an almost inevitable disaster in practice. One of two main problems is that few systems last longer than 5 years, and most can't be effectively repaired. But it is the second 'gotcha' that has got you: in-floor cleaning systems are HUGE energy hogs, often DOUBLING electrical operating costs, as well as requiring high pressure / high flow operation that can damage filters and other equipment.
More to the point, in your case, is that high pressure / high flow operation equals NOISY pump operation. Turning down flow till the heads just pop up is sort of useless, since almost no cleaning will take place. You should look up the website for your brand cleaning system; they'll have design manuals that will tell you -- in a complicated manner -- how much you can 'turn down' flow, and still clean.
You can build a pump & filter house that will reduce noise, but you have to be careful -- especially in Las Vegas -- to make sure it BOTH reduces noise AND vents excess heat. If you build carelessly, it's possible to make a little shed that will reach 200 deg F inside (killing the pump) AND only reduces the noise a little.
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The freeze thing, on the other hand, is easy. Enough flow so you can FEEL water entering the pool via the return should be fine for temperatures above 10 degrees F.
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