I have one that is similar, but without the per day fee. I have had all sorts of people drive right by it and it's on one of the gates at my driveway. Big thing. A year or so ago, had some strange guy show up, I was out with the dogs, as I came back he was just getting into his vehicle and leaving (had been at my front door). I ran into him a few days later in town, he had gotten the wrong driveway and was looking for his friends. I asked him what I could do to let people know that unanticipated visitors are unwelcome. He suggested I get "One of those signs they sell at Eich's". I told him that his passenger window was less than 2 feet away from one when he came through my gate. So.. do they work? Maybe if you whap someone upside the head with them.
I was involved in a standoff situation with some bad guys a few years ago. I was blocking their exit route and their pickup was loaded with my absentee neighbors belongings. Call was out to the Sheriff's department.. .really long story short, they got away. But the sheriff's department felt that I could be in danger, so they checked up on me with great regularity. Used to scare the crap out of me. I'd think I was all alone.. and the next thing.. here comes a deputy. I asked them to call me, I begged them to call me "If you're worried just give me a call, if I don't answer.. well come see what's going on". That no trespassing sign never, not once slowed them down. What finally did the trick was the day we only had two deputies working, one had to transport someone out of the county, and the other decided to come up and check on me. Got his 4x4 stuck at the bottom of my driveway.. which is not the best place to be when you're the only deputy on duty in the county. That worked better then anything else. I don't have a problem with our deputies, I don't do anything illegal, I just have BIG space needs and really love the solitude. Anyway.. that sign didn't work for me. If I think about it, I'll try to get a pic of one of my neighbors signs.. they work.
I also had problems with the census people. I mailed my census report in. Later found another one attached to my gate, then another, then I was coming home one day and encountered a woman from the census department just leaving my place. Asked her what she was doing, told her I had already mailed mine in. She wanted to know if the people who lived in my RV were on there. I have an older RV that is not visible from the road at any point, you have to be right on my property to see it. I asked her what she knew about my RV, she told me nothing, but that the pre-census person who came around earlier in the spring had made a note that I had an RV, so there was a possibility of it being inhabited. That made me really angry. I told her so, she told me that the census people tell them when they are orienting them that they can go anywhere, that it is a felony to do anything bad or threaten a federal employee. I filed a massive complaint and never heard a word back. Also, for those of us who live close to a border, because of the homeland security regulations there are different laws protecting our privacy.. and they don't amount to much.
I know the guy from the assessor's office in my county. He has some horror stories to tell about being shot at.. among other things. I told him that I would appreciate a call before he comes up. He told me that for people who don't let him on their property, he can only make assumptions.. so.. those assumptions are usually on the high side.
Done with that rant <VBG>
They are made just like a regular road sign, with reflective metallic paint, they say "Stay Safe, Stay Alive, Stay Out".
People do pay attention to those.