Too touristic, but what a destination!
The Old Town is fascinating, since it is still in such a good state. In July and August there will be too many tourists there. You can buy a Dubrovnik Pass, which saves you some money if you want to do the cultural stuff as well. Transport by bus is included.
Insider Tip:When you want to go to the beach, I recommend Lapad Beaches. We also visited Lokrum Island by boat (from the old town). Takes only circa 20 minutes. You can spend the afternoon there. Costs are 10 euro’s.