
I'd definitely go for padlocks, you cannot rely on people to close gates whether you have a sign or not. Today, we have the decorators painting our kitchen and I have the dogs in the office with me to make sure they are safe. I made a point of asking the decorator twice to close the front door after him, not only on the latch as the dogs can run out - he agreed and then left the door open every time he went outside.
People who are not dog people do not realise how quickly dogs can escape!
We also have window cleaner and I prefer the windows on the back to be left uncleaned if I'm not at home.
And on one occasion last year there was a young red setter (6 months old) running around on the road outside, I caught her, phoned her owners and she had escaped because a delivery man had 'left the gate open' :(