I am going to FLA for winter this year. I will turn off my water to my home, and set my thermostat at 55 for my 4 month absence. Should I also turn my hot water tank off? Or should I turn to lowest setting?
If you have good access to the pipes and can be completely sure that they're empty down to the service entry, then you can get away with turning off the hot water heater and draining the lines/tank. If it's a newer model, though, they're generally extremely efficient, and won't cost you much to leave on for peace of mind.
If you can't verify empty lines, then no, you probably shouldn't turn off the hot water heater.