Leave car outside when below freezing?

[domchang]

Was hoping to get advice/opinions from guys who drive their MBs in snowy and freezing weather.

We use stuff called magnesium chloride here in the Denver Metro area when it gets snowy/icy. Here's what I was thinking of doing with my 1987 420SEL which I am planning to use (first winter ever that I've owned it) as my snowy/icy days driving car:

If the temp is below freezing or near it, and I've been driving in the stuff, leave the car outside so the stuff stays frozen on the underbody of the car. Once the temps go above freezing then take her to the car wash and hose off the magnesium chloride asap to prevent rusting and such.

Or...

would it be better to drive her into my garage after driving in the snow/ice and knowing it's got magnesium chloride on the underbody and let the snow/ice melt off in the garage...then when the weather is above freezing, hose her off as above at the local car wash?

opinions? experience with either method?

thanks in advance

dchang