The staff at this hostel really made me feel welcomed. And for a female travelling in Greece alone that is very important. The rooms were very comfortable and clean. (That is kind of also depending on your room mates if it is clean too) The facilities they offer are great, internet, cooking facilities, laundry (expensive) and a roof top lounge. The lounge was great to relax and meet new people from around the world. Plus it has an amazing view of the acropolis!
Location is great! Very close to Arcopolis, Plaka and Monstraki Metro stn, and Syntagma Square. All a easy walk. When walking through the Plaka be careful of all the tourist souvies, really you don't need them! They are dust collectors!
Great restaurants in the Plaka and wonderful people watching too!
I felt fine as a female being on my own in Athens, metro is easy, and signs are all in english and Greek. The only people who bother you are the shop keepers in the Plaka, and if you ignore them or say you are going to meet someone and you can't talk they leave you alone. But I did get alot of offers to take me out for drinks/supper and of course didn't follow through with any.
I would recommend seeing Athens prior to going to the island so that you can really enjoy the islands so much more. Athens is dirty, smoggy and full of people. Just another big city really.