While I think it would be cool to be in Greece during the Olympics, you can expect costs for food and lodging to go through the room, if your on a tight budget Greece might best be avoided.
I think you should take the train, again if you carry the "G" zone interail pass it covers you for the whole trip it looks like. To get confirmation you might have to get in touch withINTERRAIL
phone : +49.6340.5080.397
fax : +49.6340.5080.398
And I have to say, there does not seem to be too many budget flights in or out of Turkey...
I don't know if this has helped much, but i hope it did help some...