No all night parties within audible distance when we were there last August (which was pretty much as high season as it gets out there) - just a few slightly annoying boats that circle the island with their loud speakers rabbiting on about Elizabeth Taylor staying there back in the day! They didn't bother us though, and nor did the massive yachts that again would emit some level of sound (usually awful europop disco!) as it was all daytime and believe me i am a super light sleeper and would totally have been aware of even the most distant sounds when trying to sleep.
We did come extremely close to missing our return flights though - which would have been a massive problem for us - and agree with the poster that you must allow 3 hours to return to Dubrovnik. We followed the resort's suggested departure timings for our flight (we were using the Aman transfers) and literally arrived at the airport a few minutes before our flight was due to depart (it was running late thank goodness) and after an extremely stressful 3.5 hours race against time which rather counteracted the bliss of the previous few days!!!
Did love the resort though and hope to be back!