So happy for you that Rocky is the mature boy that he is, able to be on his own now! It's always such a relief, isn't it?
At my other house, there for 23 years, we never had to post any kind of sign, the canines spoke for themselves. It was just how we wanted it, because the area wasn't the greatest, and we had 2 attempted break-ins. Only 'attempted' because they were stopped by our 4-legged security guards armed to the teeth.
Then about 6 years ago we rescued Rosco, and a couple years later, Cesar. Both very large, very intimidating-looking.... And both the most mellow, friendly GSDs we ever had! So I put up a sign on our fence, mounted on a fire-engine red board. A good friend of mine, who also had GSDs, reminded me of Michigan's VERY strict dog laws, told me I shouldn't have the sign up. I told him we needed the sign to stop anyone before they tried, because those two boys would probably open the door for them!
I do think that if push came to shove, Rosco and Cesar would have shown their GSD blood and protected our household, but I was glad they were never put to the test!