It depends on the local growing region. There's an interesting case right now on tobacco lands around Lake Erie. They're looking at using a combination of sweet potatoes and millet as feedstock for ethanol. It really depends on your local growing conditions.
This industry looks very different all around the world. On the biodiesel side, you'll end up using whatever oil-producing commodities you have in your local area. In some parts of the world, like Indonesia, it will be palm oil. For the ethanol industry, it will always be sugars and starches. When you look at places like Brazil, it's all about sugar cane, not about corn and wheat. So it really depends.
If sugar beets can be grown effectively in your area, and this is a market that makes sense, then yes, absolutely, you can certainly make ethanol out of them.