Here is some information about Meteora I was there a couple of years ago. The monasteries are in a fantastic location, as you can see from the pictures.
I’ve been to Greece but not to Athens. I was working on an archaeological dig in Bulgaria and included was a 3 day vacation in Greece while our 6-week visas “reset themselves” and we could come back without having to apply for a special extension. We were near Thessaloniki in a fairly touristy beach town.
For Thessaloniki itself, well, a bussful or achaeologists can only do 1 logical thing with 4 hours in Thessaloniki – dash to the historical museum and goggle at the grave remains of Philip of Macedon. Its not creatively displayed (or at least, wasn’t then) but its cool as shit from a historical perspective. There’s supposed to be a great open market in Thessaloniki too (didn’t see it, too busy goggling and stuffing spanakopita in my face.)
The beach town (it was in one of the three “fingers” that pokes down from the eastern part of Greece) was definitely oriented towards German tourism more so than English-speaking tourism but it was easy enough to make ourtselves understood. The beach was lovely, the hotels were cheap, and I learned how to get a cork out of a bottle of wine using only a palm tree. Life was good.
As for Greek food, I happen to like it very much but I suppose if you don’t like seafood, yogurt or garlic maybe you’re in trouble. In terms of ingredients I don’t think its too far outside Spanish cuisine with a greater emphasis on seafood and lamb. Spanakopita (spinach and cheese inside a flaky pastry) are tasty and universally available while Pastiso and Moussaka are some of the less threatening traditional Greek foods (first is a lot like lasagna, 2nd is layers of eggplant and potatoes in a creamy type sauce)
Greeks are big on sweet, milky iced coffee which they call “Frappe” – you can even get little cups of instant coffee, sugar and milk powder at convenience stores – just add water & shake! They also have Lemon Fanta (Fanta limonata) and most excellent Orange Fanta (Fanta Portokalba) which is nothing like US orange soda. last but not least, the “national wine” of Greece is called Retsina – its a white wine that is stored in raw pine barrels, giving it a pine-y flavor. People have described the experience anywhere from “refreshing” to “like licking a gym floor” depending on their personal tastes.
As far as the alphabet, this is where your high school algebra suddenly comes in useful – you will probably be able to recognize theta, sigma, alpha, beta, gamma, delta, omega and a few others. 
Enough to muddle through with lots of “Parakalo” and “Epharisto” tossed in (please & thank you)
If I had the choice to go anywhere I’d probably go to Thera where there are some famous ruins (Akrotiri) that got ruined when the island’s volcano blew – formerly called Strongyle, “The Round One”, Thera is currently a crescent shape. Quite notable is an example of second-floor indoor plumbing in “The West House” structure.
However, you can’t swing a cat without hitting history in Greece so take your pick! Oh I’m jealous!
I went there for 19 days in Aug 2003. What kind of trip are you looking for? If it is going to be a fairly tame, history-heavy kind, There won’t be much need to visit the islands, the distances will be too great and you will do OK with a bus tour around the mainland. Athens, Epiderus, Olympia, Delphi, Meteora are must sees. I went for a 5 day tour around the mainland with a tour company and they took care of me rather well, although for those more adventurous, being with a tourguide all the time might get a little tedious. Can’t comment on the food, as I am an adventurous diner, except to say that I loved it most of the time.
I spent the rest of the days bumming around the Islands, taking ferries at night. Good time if you are looking for hostels, beaches, and nightlife, but I get the imression that’s not what you are looking for.
Yeah, it will be fairly tame and history-heavy. I’m hoping the students will have time to get loose in the country some, but since they’re heavily subsidized from the University, they need to actually learn something from the experience.
You would say (and I think others too) that Epidaurus is a mainland must then? It’s the one I was thinking of cutting if I had to make cuts.
Yes, Epidaurus and the sanctuary of Asclepios is a must see. Google it for some pictues.
Also, One of the suprisingly high points of my tour was Napfilion. There’s not much in terms of classical sights, but there’s a beautiful Turkish castle overlooking the bay,and a Venetian castle on an island in the bay. The city itself is an absolute joy to walk through, not very touristy at all even during high season when I went. I cannot recommend it enough.
This is something we missed, and we hope to someday go back and see it.