A desert isn't even needed, depending on how much you need; I mined over 5,000 sand from nearby lakes with plenty more left; with Respiration III (or a potion of water breathing) and Aqua Affinity I on a helmet and diamond shovels it isn't that hard either.
In particular, I used MCEdit to analyze my world and it has about 160,000 sand blocks - despite no deserts and being only about 700x700 blocks, mostly due to a swamp; that is enough sand to cover more than a quarter of the world one block deep and more sand than iron ore (you can also see where I removed sand, replacing it with dirt, plus sand from a few small lakes where I built my base).
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So I'm thinking about making a sand generator. I know some people use them and others consider them cheaty. It's basically block duplication, which I don't really like (as opposed to a cobble stone generator or a mob farm, which I consider to be more like minecraft science). What do you guys think?