Think its clear that for the vast majority of pirates who know about the Poneglyphs, they are just about the Ancient Weapons, as Croc believed.
Probably just people related to Roger fully know that they are the key to get to Laftel(like Shanks, Inu, WB, etc). Seems like the Rocks former members all knew some things about it, its clear that BM and Kaido know the Road Poneglyphs are the way to get to the Laftel since before Roger started to collect them, as BM already had the Road Poneglyph before it, pehaps she for It from Rocks himself.
Of course some more clever guys can get that the stones have some relation to Laftel, and that's why the WG forbid them.
Law probably just got what they are about in Zou when the Inu explained it, but seems the only info he want about it is Will of D. related things. While Kid probably dont have any idea.
The thing is, as Inu explained, people only discover what they are about in Road Star, so there's no way for Kid and Law to hit it If they werent with the SH.
A cool thibg is that in last chapter the only two individual that could read the poneglyphs Robin and Sukiyaki, have meet.