How salty can snow/sleet be?
Considering there are evaporation ponds worldwide (San Francisco Bay is full of them, and Morton used to, and may still, have the majority) used for harvesting sea salt, it's doubtful that any salt deposits would end up in the Martian atmosphere. And the atmosphere of Mars is too thin to hold salt blown from existing salt deposits, so salt blown into the atmosphere by Martian dust storms would quickly settle out of the atmosphere.