In search of real Greek food (not giros on the old town tourist trail) we were recommended To Steno by a local Greek family who eat there themselves. You get a warm welcome, a friendly explanation of the menu and how the Greek 'mezedes' style of eating works and really good food. It was so good we went back and ended up eating there 3 times! Stand outs for us were the Symi shrimps (small, headless fried shrimps where you eat the soft shells and all); deep-fried, battered, stuffed courgette flowers; mashed favas ( which are actually yellow split peas, not butter beans); and the fried small fish (a bit like whitebait). When you've eaten you're brought a complimentary plate of fresh local fruit (pieces of melons, peach, grapes) to finish off. They also do really good Greek coffee.
Order around 5 'plates' for 2 people (a couple of fish/meat and 3 sides/veg) and you'll be really well fed.
Including a half litre of house wine (local Rhodes CAIR wine - good stuff) we never managed to get the bill above 35 euros for 2 of us.
This was the best Greek food we found close to the old town - lovely atmosphere, friendly and helpful staff - and the place wasn't full of tourists.
We would recommend this place without reservation.