Ios was full of backpackers and had lots of cheap, safe, fun lodging for young people.
“Far Out” had hotel/spa as well as camping facilities. We saw tons and tons of Scandinavian, Italian, German, British and a few North American kids. Lots of drinking and carrying on, especially at mid-summer, but the partying all seemed relatively innocent, and there were fun water activities on the beach, too.
http://www.faroutclu…

Now, if you seek a more auténtico experience, you might want to choose a different island and stay at a Greek guest house.