Car Rental agencies are quite few and far between in L'Escala. One of the best tips for renting a car while in the area is to get one from Girona Airport, if this is your arrival airport. The prices are cheap, the agencies are some of the most popular in the world. If you are staying in L'Escala, you dont really need to rent a car, the town is small enought that it's possible to travel around the town without the need of a car. L'Escala is a nice town, but their are many other places of interest in the close by area. A short drive away is the Marina Town of Empuriabrava, L'Estartit, and Lloret de Mar.
Hertz and Europcar are all inside the terminal of Girona airport, it's easy to rent a car. Make sure you always check out the small print for insurance excess payments and extra charges for damage and punctured tyres.