Not so much a question more a recomendation for L'Escala. I have just spent a week there with my 16 year old son and wife. I was really impressed by the beaches, restaurants, bars and general friendliness of everywhere we went.
St Marti is within walking distance which must have some of the most unspoilt beaches of real quality along the costa brava because of the restrictions that the Roman Ruins place on the environment.
For a hotel I would recommend for a budget option, the Hotel Bonaire, it's run by two absolutely charming people (with fantastic English). The rooms are spotless, the food in the bar is excellent, everything served with a smile and they are happy to offer suggestions for other places to eat or drink. If like me you need the additional room for a teenager the hotel offers great value for money whilst being only a stone's throw from the beach.