After swimming at Lake Vouliagmeni (across the street), we went to Lambros on the recommendation of a friend. The view is amazing. Although the indoor seating is excellent, most visitors opted for the outdoor seating, with the amazing views. The service was excellent. Menus were in Greek and English. My wife had fried shrimp, which was very fresh and delicious. I had a pork steak, which was very good, although the vegetables were overcooked ... likely of the frozen veggie variety. Our total, with beer, wine, bread, and cheese, was 42 euro.
Price-wise, be warned -- the seafood on the menu will cause "sticker shock" (prices 50 to 100 euro per kilo, depending on what you order. The table next to us ordered seafood (I think bream) which looked amazing, beautifully grilled on the outside. The waiter carved the fish, which was steaming on the inside, and provided servings to each person. So, while expensive, perhaps it's worthwhile to splurge a bit and share a fish with friends.
After you finish your meal, take a few moments to take a stroll on the walkway by the sea. It really is quite beautiful.