I am about to receive a latex mattress on order. Should I buy and use a dust cover on it?  The retailer suggested I should not use one, to allow for the breathable properties of the latex.

I would not recommend a water proof one for the same reason.  Although there are good natural ways to protect a mattress from the accumulation of mites, washable wool filled mattress protectors are my #1 recommendation for price/ease of use among other benefits.  There are also full mattress encasements available that are completely mite proof and made out of nothing but cotton.  They just will not do as good of a job keeping perspiration and oil from the mattress core as well.  What latex mattress did you order?

I ordered from Custom Sleep Design

I would recommend the St. Dormeir Mattress Protector, I didn't find any literature about what is covering the latex cores other than a cotton cover.  You will want a breathable protector but also something that will protect the latex from your perspiration, wool is the easiest way to do this and the next cheapest outside of waterproof protectors which are not comfortable at all.

I personally found some of the thinner polyurethane membrane/terrycloth protectors that are waterproof/breathable work quite well (was using one before I got my wool natura). While I personally like sleeping on wool, it does change the "feel" of your mattress more than the thinner protectors. They are also dust mite proof. I would tend to use the top/side version rather than the encasement though and perhaps that's what the retailer was referring to (encasing the mattress with one of these would offer better protection but diminish it's ability to breath). They are probably not as breathable as wool either but they certainly didn't give me any "problems" that I noticed either in terms of feel or breathability. You can get them in two layer versions and 3 layer versions (terry on each side of the membrane). I guess it would depend on how important the different options were to you (feel, water resistant/proof, breathability, natural materials, etc) and which "tradeoff" was more important to you. I think it's very important to put something over your mattress and I can't imagine that he was suggesting that you sleep on the bare mattress with just sheets over.

Phoenix