A "No Trespassing" sign might work better than the "No Solicitation" one. Also, just like with the phone calls you could politely ask that the people that come to your door make a notation that you don't wish for them to come to your home. I know that is an option for some of the religious people that stop. Or you might try just listening to them once. They aren't coming because they want to bother you but because they care, even though you may not see it that way. Just think of it from their point of view for a minute. They aren't getting paid and are actually expending time, effort and money themselves. Why would they be willing to do that? Perhaps you could ask the next one that comes and listen to the answer they give. Or just go with one of the other options listed.