When are you going? My son and his friend cycled from UK to Turkey this summer and camped most nights. Once it was September most of the Greek camps sites were shut and they camped on beaches. They really loved Albania where the people were so friendly and they camped by restaurants and bars. They didn't book anywhere in advance and had no problems finding places anywhere on their route. Hope you have a wonderful adventure.

our favourite place akyaka has a small campsite, this is about 20 miles from marmaris, akyaka is very scenic but quiet so depends what you are looking for, but might be a good stop off point , its called Akyaka Orman Camping, this is the only link in english i can find, but maybe if you have a good search you might find more info

http://books.google.com/books?id=r0_gJ7wEXWsC&pg=PA251&lpg=PA251&dq=Akyaka+Orman+Camping&source=bl&ots=gXc83c9yfM&sig=Mcp_WU_fqn73yO-Kyeeb3efn-I8&hl=en&sa=X&oi=book_result&resnum=6&ct=result

Look here for a very nice camping on Datca near Marmaris:

http://www.marmaris-datca.travel/Aktur_Camping_Lodges

rgds jeroen