Bill, I have let some use my property with certain rules. It seems that no one knows how to follow the rules. One asked to go and look around I told him that was fine just do it in the summer because I hunt. I found out later that he went during deer season. Another, I was letting her and her daughter ride horses. I asked that they let me know before they did because I might be hunting. I also said not to go on the other neighbors property that joins us without checking with him. They broke both of those rules plus took about 6 other people with them across mine and the neighbor's to a cave. This was while I was hunting. I found out later. It would be fine if people could follow simple rules. These are the neighbors that I am friends with I won't even get into the bad ones.
Given all you've said, here is what I think I would do. First I'd write a letter and send it to all of the folks whom you've given permission. The letter would be very polite and simply say that in the past, you have given permission to a number of friends and neighbors to use your property under certain circumstances with guidelines. Recently you have realized that you have overextended yourself a bit granting access to the point where it is having a negative impact on your own recreational use of your land. For now, you are rescinding all permission you have granted for others to use your land. Say you plan to take a year or two to see how this affects the wildlife on your land. After that, folks are welcome to ask permission to use your land again and you will be happy to look at each case and grant written permission again where appropriate.
Next, I would put up posted signs.
Anyone who trespasses after receiving this letter deserves to be prosecuted or at lest confronted depending on your relationship with them. Then take that year or two and see if it really makes any difference to you. If so, when folks start asking permission again, grant it for those you deem appropriate but grant it in writing. Include any guidance as to when, how, etc. they may use it. When something is in writing, folks take it more seriously.
My guess is that in the end, you will get your message across without causing bad blood with neighbors and you may even end up with better understandings of each other and better relationships.
Also, consider adding your general location to your profile. For example, if you were in my state, I could provide much more specific guidance on the laws and tools and how to use them effectively. It is also important information for answering questions on foodplots and trees and such.
Thanks,
Jack
