Possessive or Just Plural?

n2, I'd'v writ "Visitor's"

But sorry, that's an opinion

However these days in titles of this sort the apostrophe is often omitted altogether

That's a start, thanks!! Any others?

Possibilities

1. The Visitor's Guide...A Visitor's Guide

2. Visitors' Guide

3. Visitors Guide

1. The meaning is, a guide for the individual visitor.
2. The meaning is, a guide for all visitors

both of these are "correct" grammatically. The choice depends on the meaning you wish to convey.

3. This gets away from these niceties, is rather informal, and this form would be adequate for an advertisement, poster or pamphlet.

Great, thank you!

So I guess they're all "acceptable" if used as the title of a Visitors' guide.

I'd say so.