I have caught a lot of people using the outdoor water faucet where my garden hose is attached. I actually had to use something like this to lock a faucet that people were using at one of the apartment buildings I work at.
There is no walkway between my place and my neighbor, so anyone who is using the faucet is walking through my yard. You should be able to install a shutoff on JUST the line that goes to the outdoor faucet, so that it doesn't affect the laundry room. But I do know that to turn on the water valves at school you needed a square water key. Is the landscaping and pest control provided by the facility? I don't want to turn off the water line because it is also feeds into my laundry room. It was not as big and bulky as the one linked above, but it worked in a similar way. Anyway, is there any kind of locking device I can put on there so that it is not accessible to others? Having never paid anyone to do my landscaping I don't know them.
It's fairly small, just screw on the brass piece, cover it with the chrome cap, and lock! EZ-FLO 20215 Female Loose Key Hose Bibb something like this landscaping company is liable to have a water key, though. The shut-off goes INSIDE. What he said, just install a valve in the line before it goes outside. The faucet is located on the side of my condo. I work at a tree service and our contracts state we may need access to water and electricity. You might want to look into something like this: just goes over the valve handle so it can't be turned. Then maybe the lock is the better way to go. I'll look and see if I can find what I'm thinking of online, but they're out there!