Dewinterize when you reach a place that is not freezing at night. It is really a matter of the water lines location, including your low point drain. Where they are located in relation to heated space in the RV, If they are all in compartments that are warmed at night by your heater then you can flush out the antifreeze as soon as you are where the temps stay above freezing in the RV while you drive.
Do not leave your water hose out and hooked up in freezing weather. Use you fresh water tank water and refill it as needed in the daytime.
You have already received good advice on the sewer hose, look into a spare 20-30 amp plug adapter in case you find yourself only able to hook up to a 20 amp pole. Have a few 2x6x12's available for side to side leveling, take along chokes and always use them. Most folks use a hose rated for human drinking water (generally white in color) but a spare short hose and a Y adapter for the faucet will come in handy too. There are probably 20 other must haves I forgot but someone else will mention. Have fun and the temp is going to be 70 degrees here in NM on Wed :)