The cruise we are taking arrive in Athens at 8:00 a.m. until 6:00 p.m. Does anyone have a recommendation for a guide or should we go on our own.
That's the $64 question, isn't it? If you first determine what you want to see you can then decide if it's easy enough to accomplish by yourself or if you need someone to help you through the process. Have you figured out your 'must-sees' yet? If you want a guide do you want a driver or will you be taking taxis? Do you have a maximum budget for this? If you decide on a guide, once you have answers to these questions I recommend you contact Fantasy Travel or Dolphin-Hellas Travel, both in Athens, to ask them to help find you a guide/driver.
These are two highly-respected and very reliable travel agencies.
We think that a professional guide is usually money well spent. One who is recommended by the agencies above should be fine.
Athens has a lot to offer and your time is very limited. Its a good idea. Possibly someone from your cuise will want to join you, reducing the cost.
Depends on what you want to see. With 10 hours to spend, I would take a taxi from Piraeus, first to the Acropolis/Agora, second, the National Archeological Museum, then use any remaining time to walk around the Plaka. You don't need a guide for these sights. (Note, you can take the Metro from Piraeus to Monastiraki for €1, but it could be a long walk from the ship to the Metro station depending on where you dock. A taxi will cost around € 20-25. Ask about the fare before you get in.
We wished we'd had a guide for the Acropolis. But only a good guide (like the wonderful guide we had for our tour--with Key Tours--to the Peloponnese and Delphi) and a small group.
It seems like the cruise ship might offer various tours for passengers.