Your biggest problem will be dust and clay particles. A Pentax 6x7 is plenty rugged, but handholdable only at moderately high shutter speeds with normal or wide-angle lenses. But the curtain shutter plus mirror will get any dust pretty well dispersed inside the camera. The same would be true to an equal degree for most med format cameras. So you need to take extra precautions when either changing lenses or film, to prevent dust from getting inside. You'll want a soft dishcloth sized microfiber cloth and mist bottle to wipe your camera down before opening it, preferable a distance from all the ruckus, mabye inside a disposable plastic trashcan liner, or at least upon a clean elevated surface. Hard to do under such circumstances - but if you're happen to especially enjoy spotting images afterwards, this event should be heaven. Sand and grit can obviously mechanically affect your lens too. Might want a clear filter over the lens unless it's a clunker you don't
really care about. But I'd disagree about Bill's comment about larger formats and dust - the more film area, the more electrostatic surface
you have to attract dust, esp if you pull a darkslide.... such things need to be coated with antistatic sprays prior to the trip; and in desert
conditions I've sometimes even taken along a length of speaker wire with a tiny alligator clip at one end and a nail at the other, in order to
ground metal cameras (it actually helps when working from a tripod)... motor winders are about the worst thing I can think of for shooting film in the desert per static attraction to film .... so even when manually advancing film, don't do it too rapidly. And with a big rowdy crowd,
you have to consider not just physical damage to your equip but potential theft.... in other words, don't take your best gear if you have
another option.