water leak underground
You definitely want to turn off the water supply at the demarcation point where your responsibility begins during times that you do not need the water service.

Last thing that you would want to be surprised at would be to receive a water bill notice for $940 when you have been away for three months. I had that experience once when I knowingly had a cabin side shutoff gate valve that would not shut off completely due to sediment deposits in the pipe/valve. I had taken to turning off the water supply at the street by the water meter when we left this mountain property for a long period of time. 

Also it was always advised to leave certain valves open at the back of the cabin during cold weather to drain the water lines to prevent freezing of the water lines under the cabin. Well it turned out that an industrious water meter reader turned the valve back on at the street when they found it off. Needless to say this caused a huge amount of water to flow until a couple months later when I received a gigantic water bill in the mail. 

In the end I had to take to installing a padlock on the main shut off valve to prevent a repeat of the problem until I was able to flush the water lines to get rid of the sediment in the gate valve by the cabin.