There is no way I can keep current with all the theater stuff going on so its up to you! Have fun I know I have! Check out these very few sites that may tell you what you want to know! Look for the English language button, usually a flag.
Try copy pasting, as I refuse to hot link, as some of them crash my computer so go at your own risk.
www.nationaltheater.gr | www.theatre-museum.gr | www.theaters.gr | www.megaron.gr
Very limited "in English" theater performances are held at the Odeon Of Herodou Atticus where are also held dance and musical performances. www.hellenicfestival.gr
Still, the Odeon is a cool ancient venue sheltered by the Acropolis and I recommend it! Tickets may be bought only 3 weeks in advance and sell out quick as it only holds 5,000.
This is the pre-eminent Theater/Odeon of the western world! The Odeon of Herodes Atticus is over 2,500 years old and was the first major odeon ever in the Western World! What exists today has been rebuilt by the Romans who used to flood the theater and have mock sea battles staged! What boors! How gauche! Attending a show here is a real treat and you will always remember you were in Greece after you have attended one!
The sheer number of small theaters in Athens is pretty staggering really if you think about it. There are scores of them! How can average Greeks afford to go to the theater if the economy is so tattered? How can they generate enough ticket sales to pay pay the actors, producers and directors and still survive? Good question! Many don't!
There is money however for state and private run TV and these big players need a talent pool from which to draw. They subsidize the theater. Its stiff competition however. I personally know trained theater people and choreographers who have given up long careers in theater and performance arts because the money is very poor. Greece is a small market even with 5,000,000 diaspora Greeks who can shop on line. Singers do better than actors in this regard as its expensive to digitize a play and stream it to Melbourne, Astoria, Queens and Greek town in Chicago or is it?