EP, i am excited for you! I went to Olu Deniz last summer (my first time abroad anywhere) and it was just amazing. The first sight of Olu Deniz beach with the boats moored blew me away. To be honest i didnt like Hirasonu but then i am not a nightlife person.
I enjoyed evening sitting on Olu Deniz beach at the Buzz Bar (think thats what it was called anyway, my memory is not to good). Also Sugar Beach on the other side of the lagoon was nice place to hang out.
Highlights for me were; Dalayan river trip, Fethiye market, Kaya Koy, Jeep Safari (totally crazy), seeing hubby paraglide. My favourite places for eating in Olu Deniz were The Turkish Pizza (for lunch), The Pirates (now Pine Tree i believe) and Captain Hooks. But Fethiye was the place for doing it eating as Maverick says.
The best bit of Turkey was by far its people.
I spent two weeks there and have felt homesick for the place ever since. Truly you are going to have a great time.