I have no minimum. No particular maximum, but just not too expensive. Such as no more than $75 with all charges for dinner for 2 and 2-3 glasses of wine each, without dessert. (From what I see, prices seem analogous to U.S. ,but if I am wrong, adjust price accordingly.)
Looking for authentic meals with hopefully interesting but traditional cuisine in a place not overrun with tourists (like myself!), but absence of foreigners not necessary. Sometimes places too promoted in guidebooks cater too much to tourists but I may not know to find them on my own.
We will be staying just south of the Acropolis Museum and Metro stop. All things equal, would prefer to walk to dinner, but would travel if worthwhile.
I would agree that you should surely avoid the most touristy restaurants in Plaka, Monastiraki, Thiseio, as they are expensive for what you get(pretty much frozen food).
In Greece the expensive restaurants usually serve foreigh inspired food, so I wont mention any molecular, frech haute cuisine ones with stars or not.
I dont live in Athens, but I visit it often, so I ll speak about the places I have chosen to eat thus far.
As you will stay near the amazing Acropolis Museum, you can have a lunch there. The cooking is Greek, not excellent but I found it pretty good. You can see a small sample here http://gastrotrips.blogspot.gr/2013/09/acropolis-museum-athens.html
In Thiseio, there is only one restaurant worth mentioning called Kuzina. What worths is the view from the opened terrace with direct view to the Acropolis. Food is modern. I suggest you make a reservation before the meal. 4 course menu for lunch (only i think) was 20 euros pp without wine.
In Chalandri there is a restaurant called Psomi & Alati, by the chef Yannis Loukakos. It is a bit far from your hotel though. In chalandri there is also Botrini's restaurant, starting at 40euros pp.
In Hilton hotel there is a seafood restaurant called Milos Estiatorio. There is one in NY too. It is expensive generaly but there was a good lunch deal at 20 euros pp. I hope it still exists.
Aegli Zappiou, http://www.aeglizappiou.gr/estiatorio... , excellent location and setting, pretty much close to your hotel. You can also see the menu with prices in their site.
If you decide for one meal that would be more expensive, there are 2 restaurants that come to my mind with Greek food. One is Varoulko (1star) by Leuteris Lazarou serving seafood, and the other is Tudor Hall by Sotiris Euaggelou (havent visited but had a meal by the chef and it was amazing). I consider them to be at 50 euros per person without wine.
Wine in Greece is good. (Avoid not bottled, it can be very good but most times is rubbish). I hope they can advise you correctly on what to chose according to price.
In all of these restaurants you will not find mousaka etc, I think these are only for tourists, so available only in places that work 99% by tourists.
Gyros, souvlaki etc, as for greek fast food is on the same level in most places, so just go in what you ll find on your way.
If you find any greek casual taverna, the pricing is about 15 euros pp, but only if you avoid the touristy areas.
In the islands that you mention, keep in mind fresh big fish can be at 60 euros a kilo, I have seen 80euros too. It is delicious though.