It's nice that you have your property posted, but the guy is in the truck, and I'm guessing that the dogs can't read. You might need to do something a little more than putting up signs if you don't want the dogs on your property. Where I live, you can put up all the No Trespassing signs you want, but if some idiot ignores the sign, goes on your property and gets injured, you're still liable. In other words, signs alone don't mean squat. I hope you can get your rights figured out.