I must admit we have been to Fethiye for several years now and never bothered with a car hire because the little dolmus buses go everywhere even back into the hills and other villages.
They are so frequent and seem to stop anywhere and only cost a few lira at a time.Local travel with the turks is fun, bustly and you get into the Turkey mode as opposed to being separate in a car.
Fethiye district is huge and well served by the dolmus.
We ended up not seeing much advantage in a car at £30 a day odd.
Just an opinion and an alternative view!!
Best of luck anyway and enjoy the holiday