I've shot LF in some pretty dusty sections of desert and been OK. Not in sandstorm conditions, obviously---you don't want your cameras exposed at all for that stuff! But in the usual conditions of wind gusts that occasionally kick up a dust devil, I would expect you could get away with reasonable caution: keep equipment in a box or something when not actually in use, wait for a lull before putting the holder in the camera, keep the lens cap on whenever you don't need light to get through. It might be best to minimize lens changes too.

I actually think a folder might work out well, because of the simpicity (what's the sand going to do, clog up its autofocus?) and the quick transition from folded-up to ready-to-shoot. Keep it in a bag or a big pocket or something, maybe a gallon-size Ziploc bag if things are really bad, and find someplace good and sheltered to change film (maybe inside the car).

Desert scenery can be tough because of contrasty light and low-contrast subjects (beige rocks, taupe rocks, ecru rocks, and tan rocks all look much the same to b&w film). I guess that militates for a film with a large dynamic range but a fairly steep curve in the mid-to-upper range, which does sound like TMX/TMY, doesn't it? Or maybe TXP.

-NT