We were there last 2 weeks of October last year and it was lovely, still as hot as it was first 2 weeks of June but not the intense power in the sun - as in we didn't burn or need high SPF - infact we didn't use much lotion at all in October

but we still came home with lovely tans.
It was cold of an evening tho, we had to ask for blankets on the bed and the temp dropped quite quickly of an evening but just chuck a few cardies or light jackets in your case and you'll be fine.
We had a day or 2 that was cloudy so we took advantage and went exploring the old village and did the walk to
Marmaris a couple of times.
It's lovely and peaceful in the day but still quite lively of an evening and all the restaurants/bars and shops all reduce their prices to try and get rid of their stock so there's LOADS of bargains to be had - barter, barter BARTER !!!!!!!!