Hi,
You will be quite surprised at the prices, shop around and you will get some great meals, try and go where there is a menu of the day as that is normally about 10€ pp and includes 3 plates water and wine (lunchtime)
However depending on where you are staying you will will find some great restaurants.
One of my favourites is the Tivoli Terrace in the Bellevue road, it is right opposite the bellevue complex by the chemist and has a band on singing at night but also a small childrens playground at the very bottom where kids can play quite safely. The food is fab and the pizzas are amazing as well as the kebabs sticks. Cheap and friendly, you can't go wrong.
Another brillant restaurant is "La Villa" in the port, this is a chinease in front of the taxi rank and it really is the best, not the cheapest in town but I would recommend it.
There is a lad called John who has worked there for 6 years and knows the menu like the chefs!
Regards