We were there from 4th -20th and we didn't find it that quiet in fact the Champagne Bar, Richards Place,Wonderboys,Amigoes.Elvis Bar etc were all full and everyone was having a very good time,the restaurants were also pretty busy as well.
spoke to turkish friend of mine working in very well known hotel he say tourism very low/quiet his work season finishing early this year he also works bar street clubs in his spare time when i was there in july i borrowed his pushbike and rode from marmaris to ishmeler and back on the coastal footpath there were very few people to be seen even the beaches were quiet
We were there from 4th to 18th and it was quite busy at night but during the day was quiet but I expect it was because it was so hot people were chilling by the pool.
We just got back last night.To be honest we found it quite now in saying that some bars were packed but there was an awful lot who were either empty or had only a few people in them.