I would head to the Pink Palace on Courfu you cant bet it for a a good time and value for money, like Petersmith says heaps to do during the day and something diff on everynight at the nightclub, toga parties, uzo ciclres. Plus you cant beat it for value 25 euros a night for an aircon 3 ppl share room, with own bathroom basiclly like a cheap hotel room plus a 3 course dinner.
I was over there in July last year and you can get a return ticket to courfu from athens for around 45 euros i think it was. Hostel Aphrodite is where i stayed in athens and the bus left from there, 8 hours by bus then 3 by ferry to get there.
I also went to ios and courfu was deffinetly betta i would have to say, ios is still good but its totaly different more expensive plus its not really that good a place to meet ppl its more full of ppl travelling in groups on a 2 week benda. I stayed at Far out camping in a tent which i wouldnt recommend, nightlife only picks up after midnight and its too hot to sleep during the day, i only lastest 5 nights.
Anyway where eva you end up going u will have an awersome time let me.