I would like to take the metro from the Airport to Acropolis Select Hotel - but am very confused as to which stop to get off at.

Also - we will be arriving at the airport at 10:30 pm. Will the metro be running that late? What is the schedule.

As an alternative, how much would a taxi cost?

We just returned from a stay in Greece, with a couple of days in Athens. Although I am not sure about the exact location of your hotel, if it is near the Acropolis, the Acropolis Station stop on the blue line is probably closest. Problem is that the Metro probably won't be running at that hour. I think that it stops at 10:00 pm. Taxis are pretty expensive (it's supposed to cost between 24-40Euros, but cost us a bit more when getting service in the middle of the night). We took the Express Bus #95 to the (last) stop in Syntagma Square, right from the airport. It's convenient and certainly a lot cheaper than a taxi and is supposed to run 24 hours a day. Just be sure to purchase bus tickets (3.60 Euros per person) BEFORE you get on the bus, since they don't sell them on the bus and you can be fined for not having a validated ticket on your person.
You might want to check with your hotel, to see whether it's reasonable to walk with luggage from Syntagma Square to your hotel. We walked to the Plaka area from the square in about 10 minutes. Seemed like a pretty safe area.

Does anyone know where I can get a schedule for the Athens Metro system?

The bus drops off at Syntagma Square - but that is not anywhere close to our hotel.

Go Here: http://www.ametro.gr/index_flash.htm#

Click on "Metro Operation," then "Operation," then "Train Service."

hmm - that is exactly what i was looking for - thank you