There has been a proposal that we add significant signage the has all
the "No's" on them.

No Fishing from the piers.
No swimming.
No Trespassing
No Parking unless member or guest
and so on.

Put up a sign in each area where it's appropriate. Put up one sign listing
them "all" in a place where most foot traffic goes through. Just make sure
the signs are in keeping with what the area. Don't put up some ugly-ass
metal sign when everything else is in carved wood, for example. It really
depends on the layout of the marina.

If swimming or fishing from piers becomes a problem then consider a similar
sign at a the place where it's problematic. But above all, be consistent
and be even-handed in enforcing it. If a non-member isn't following the
rules you're going to have to speak with them and ask them to leave. Most
folks would will go without confrontation when it's not started as a
confrontation. Some won't and that's what the local cops are for.

In actual practice, other than fishing from the piers, there haven't
been a lot of problems so I am really just asking, what creates a
better image for the marina. Lots of signs or few as possible?

I think that signs at/near the entrance or main 'choke points' of foot
traffic are better that ugly signs tacked up all over the place. A few
well-placed signs combined with pleasant, but consistent enforcement are
usually the best.