You should expect to find that all the street signs are in Greek.
You should expect to find that very few people outside of the touristy part of Athens speaks English.
You should expect to find that the roads in Athens and elsewhere are incredibly difficult to navigate as traffic is heavy and the number of one way roads make Atlanta look normal.
You should also expect to find the most amazing place you will ever visit in terms of historical significance and beauty...both in architecture and nature.
You should go see the Acropolis, the Navel of the World at Delphi, the battlefield monument at Thermopylae (where 300 men stood between our history and that which would have come). You should see the seashore and the islands (on your second trip if the first is too busy).
You should be ready to encounter a people that are initially stand-offish, but who are warm and humorous, kind and helpful to strangers, willing to give directions by hand and arm signals (and drawing in the dust on the ground) to the spot you show on the map as long as you are smiling with them.
You should be prepared for an incredible jousney. Have a great time.
Get a guided tour through Athens.....IM
me if you want a referral.