I've cycled most of the western and southern coastlines of Turkey from Tasucu in the south to up past Gallipoli in the North and into Bulgaria. If you like climbing then there are plenty to go at along the coast. You will find a lot of roadside water taps along the way to keep your bottles topped up and it will be needed on the big climbs in hot weather. The main road D400 is fine for cycling along. Just take care around Izmir as it is all a bit hectic entering and leaving the city. There are cycle paths along the city foreshore and ferries are available to cross the bay. Accommodation along the way is cheap and plentiful if you need it. I used budget hotels on tour from Antalya to Tasucu at around a tenner a night and also stopped at Calis Beach in Fethiye, Kas and Ayvalik. All clean, basic and good value.
My ride from Antalya to up past Izmir is covered here:
http://www.crazyguyonabike.com/doc/codheadontour2015I've done Marmaris to Antalya and Antalya to Fethiye sections as well on previous tours and thoroughly recommend the Turkish coast for cycle touring. There are plenty of resources along the way and I never hand any trouble at all from the Turkish people. Quite the reverse in fact. I found them to be very friendly and supportive which didn't come as a surprise as I had a villa in Camyuva near Kemer (south of Antalya) for 6 years so had done a lot of acclimatisation along the way. The food is wonderful and cheap. Nice and fresh and very tasty. One of my favourites is Tavuk Sis which is chicken kebab. It is basically grilled chicken on skewers with bread, rice, onion and salad. Lahmacun is also nice. A round, thin piece of dough topped with minced meat and minced vegetables and herbs including onions, tomatoes and parsley, then baked.
There is a big climb out of Kas and also a big climb out of Kumluca heading towards Antalya. My favourite section is probably Fethiye to Antalya. When you get to Camyuva check the maps as minor roads can be taken heading towards Antalya to keep you off the D400 as it starts to get busy from there with a series of tunnels. When you get closer to Antalya you will have to rejoin the main road.
Good luck with the tour.