A little bit of everything...
I was a bit sceptical to Rhodes before I went there- it has been a charter destination for such a long time and I figured it would be over exploited. However, I was surprised it could offer so many beaches and visit worthy things off the tourist tracks. Even if you go to Rhodes during the peak season you will be able to find more or less deserted beaches. And if you have a car make sure to drive along the west side through the villages - it is very local.
If you're looking for more crowded places and other tourists you won't be disappointed. Stick to the old town, the bar streets, the huge hotel complexes and the beaches closest to Rhodos (city) and you will find plenty of people. Rhodes simply offers a bit of everything. For everyone.
