I bugged out of Laramie on Saturday evening, and glad I did. They had about 6" of snow at the CG by 8:00AM and roads were closed. I didn't want to deal with traveling 287/I-25 in the storm with the PUP attached, much less burning that much propane to keep it warm (in addition to running the electric heater non-stop).
I keep the PUP in the garage so I didn't bother to winterize. But as to the original question, blowing out the lines and adding antifreeze to the drains should be good for the short-term, especially since it's not much below freezing. When I've been camping with sub-freezing overnight temps, I disconnect from city water/turn off water pump and open the low-point drains. Open the faucet to allow air back into the system. This has worked well for me many times over the years.
On the bright side, It's supposed to warm up tomorrow!
2004 Toyota Tundra SR5 (V8, 4WD, TP, TRD)
2005 Fleetwod Allegance with axle flip
Honeywell 2000i Generator
Me, DW, DS, DD, & Chicken-Dog