Even though the winterization port might be hard to get to there are other things you can do in a pinch.
1. Open the Low Point Drain (both hot and cold....on my SV34 the Low Point Dran is the outdoor shower).
2) Open every faucet in the coach to let the water drain from the lines..... being sure to alternate between hot and cold with the inside faucets so both lines drain.
3) Get this blowout plug and install it to your city water port and then blow out the lines with a compressor set at about 40 - 50 psi.
4) Drain your fresh water tank as well as black and gray tanks.
Even if you can't add RV antifreeze this can prevent damage. Bursting is caused when water lines are full and pressurized such that once the water starts to freeze and expand, it has nowhere to go so the weakest areas will split.