Hi Sirkyboy,
I've hired a bike a few times, tho only for a day or so at a time. We always stay in the old village, so it's good to have something to buzz around on, and the ride over to
Marmaris is great. It's a full 6.5km over there though it doesn't feel it! Not sure on the prices for two weeks, but I'm sure it'll be relatively cheap. Most bike hire places will include a lock too, so you can lock it up at your apartments. It's worth checking your apartments too, as some (Moonlight, for instance) have a selection of bikes to hire.
For extra, and slightly quicker fun, last year I found a place that hires out electric scooters. Not the two seater, three wheel types, but just like a normal scooter only electric. I hired it again this year a couple of times. 70tl for 24 hrs! £18!! Considering the three wheelers cost 30tl per hour, that's a bargain!! As I say, good fun to buzz round on, and a great way of getting a breeze going!!
Hope you enjoy your holiday, mate,
Paul