Didn't take any gear in the end and we were always too close to the sea- I didn't see anything worth looking at from Split all the way down to Dubrovnik - I think most the thick chunks of limestone with oles' in are up near Vukovar (?) in the North East of the country.
On a separate note, If you are in the South and have a hire car, it's really interesting to go into Bosnia and the hills look quite impressive the further in you go- just don't wander off the beaten track in remote areas as they haven't cleared all the landmines yet..., Monenegro is also worth a look but the road there is quite busy in the summer.
Let us know if you do go caving there.