I don't have a letter, but I was always a stickler on this one. I suspect it depends on where you are. In the U.S., it's like this:
- "No trespassing" on a personal residence means you're on your own if you ignore the sign.
- "No trespassing" for a community (e.g. apartment complex) means to tread carefully, and if management asks you to leave, to so immediately. The law really does not permit management to speak for the entire community. Only if the sign is at a single resident would it really hold any legal weight.
- "No soliciting" means nothing, really. If it says "no distribution" or "no religious groups," it's still not the same, but at least it gets the message across. There's no legal issue with this one, as far as I know.
Now, that said, our last CO talked specifically about "No soliciting" signs, and basically said that most people think it means the same as no trespassing, so just use caution. Maybe ask the householder if the sign applies to JWs.
I came across a door once where there was a "no soliciting" sign, but it was above me and off to the left-hand side of the door. I never saw it. The householder opened the door and pointed to the sign, at which point, I had to look up to even see it. I apologized and went on my way.
In short, "no soliciting" is not the same as "no trespassing". Best you put up your own "no trespassing" sign on your door, if you live in an apartment complex.
The only one that bugs me is the "no canvassing" ones. Some communities have a "no canvassing" ordinance. I talked to one of the elders about this a year or so ago and pointed out that when we go and leave our tracts, like for the convention or memorial invitations, we ARE canvassing. There's no two ways about it. We MUST obey the law. The elder didn't see it the same way I did.