Do you want a resort catering to foreigners with lively night life and lots to do or somewhere out of the way with no mass European tourism and a laid back atmosphere? Are you interested in the Turkish culture and history? Are you interested in water sports? There are many lovely resorts in Turkey to suit all tastes.

Nightlife but not 18-30 and do like to do some sightseeing,

I was thinking Iclemer but not sure as don't know much about turkey.

mari,

You may find members Resort Reports useful. Icmeler would probably tick all your boxes, but there's plenty of other resorts too.

Darren

Maybe Gumbet would suit you, it can be very lively mid season but May it is nice, good nigtlife but not all 18-30 that time of year.

There is plenty to see around the Bodrum Peninsula too.

Icmeler and Turunc are nice. Both resorts are popular with Brits and there is the opportunity to travel from them to quieter areas such as the Bozburun peninsula. If you are adventurous and prepared to DIY, the Datca peninsula is stunning and the town of Datca itself has laid back night life but with no mass European tourism. Even in high season you will find uncrowded beaches and fascinating historical sites.
The Bodrum peninsula is also very nice with several very nice resorts although much busier than the Bozburun and Datca peninsulas.

Wherever you choose you will find that getting about is very easy as the transport systems are very reliable. If you decide on Icmeler for instance, you will have the benefit of being able to see some quite different resorts such as Marmaris, very busy, lots of shopping, lively nightlife or Turunc very villagy and laid-back with some great restaurants. You can also get overnight trips to Ephesus if you want some culture, or white water rafting on the Dalaman river if you're after a bit of excitement!
Other nice resorts are Dalyan or Akyaka if you want lovely sandy beaches.
There really is something to suit everyone, and you'll find the Turkish people very welcoming.