Before a trip should I turn off the water of my house?

If no one is using the water in your house, the traps will dry up even if you leave the main water valve on.

I don't cut mine off because my daughter & grandkids make stops there every few days to check on things & often use the facilities, water plants, etc.

But if no one is in the house at all, definitely cut off the main valve and pour some vegetable oil in the traps to keep them from drying out. That's the cheapest thing to use.