"I don't think that this is contingent on variety, and judging from their rapid verticle growth, doesn't seem to require even a semi-dwarfing rootstock." This is exactly wrong. It is very dependent on variety as a Braeburn or Empire on M7 will perform very, very differently from a Mutsu on the same root. The Braeburn could easily be permanently held to seven or eight feet on my soil. The Mutsu could easily turn into a twenty-two foot monster in just five years. Where I am those four feet spacings are m9 or similar depending on variety and soil. those varieties being Jonagold, Gala, Sonata, or similar. If you see those tight spaced orchards with vertical growth then they are doing it wrong. You do not want vertical wood. Google "French Axe". Those orchards take much labor and investment in trellis to achieve early production. One mistake, resulting in a missed year of early production, and you are behind the curve in return on investment. Some say you will never catch up. In fact some say that those tight spaced orchards with their required investment in labor and trellis are already uneconomical. It is like housing milk cows in year-around barns. Its time came and went very quickly. According to the main Michigan State University dairy prof, those methods are not justified financially. Enough digression. Do as Squeeze states and use the ground you have. And if you are dumb enough to use MM111 in a high density then you deserve all of the headaches you will get.

I'd look for commercial or pick-your-own operations nearby, and ask them about what does well there. You can grow the trees most anywhere, but getting fruit is a somewhat different proposition. Good farmland with good soil, not in a frost pocket, adequate water, good roads nearby...I'm sure you'll get lots of advice. Your County extension agent would be a good person to talk to.

Goldrush won't get to quality there most years, I suspect, and second the suggestion of Ginger Gold which is rapidly becoming the most popular golden around here. It's extremely grower friendly in being precocious, strongly annual bearing (when properly managed) and a very long harvest period, starting shortly after Williams Pride. WP is a great summer Mac type but if you want a summer golden run with Pristine for scab resistance and a pretty good summer apple.

The little bit of heaven I live in is in Southern Utah, St George specifically. Its a desert climate and we've never used any fungicides on anything - its so dry here. The tops of the fruit trees occasionally sunburn but no harm underneath. We (meaning me and my mom) had a beautiful yard full of fruit and nut trees before I got married and moved to my current teeny tiny complex yard :). The orchard I am planting is in my mom's older next-door-neighbors yard. They only pest we had on our fruit trees were birds when the fruits were ripe. But we invited the birds because they ate the bugs. They deserved a treat. :) And any fruits that fell to the ground were cleaned up right away by these two little rodents, Brody and Camo: But there are things we can't grow. It's TOOO hot for cherries and certain varieties of apple. And not nearly enough chilling hours. And I love cherries :(