You’ll definitely see much more of the Costa Brava if you are travelling around by car, so unless you’re coming for a pure and simple beach holiday (and are happy to stay around one or two specific beaches) or aim to spend a lot of time walking, I’d definitely recommend hiring a car.
Cars can be hired from both Girona and Barcelona airports (where you’re most likely to be arriving) as follows:
From Girona Airport
Europcar. (902 105 055; www.europcar.es), Hertz (97 218 6619; www.hertz.es), Atesa (902 100 101 (Girona airport office); www.atesa.es), Avis (97 247 4333; www.avis.com), Auriga Crown (972 474 617; www.aurigacrown.com) and Economy Car Hire Girona (+44 1362 853938; www.economycarhire.com/gerona).
From Barcelona Airport
Hertz, Avis, Atesa and Europcar. Contact details as above.
The other advantage of having a car around this region are the spectacular coastal roads. These easily equal anything on the Côte d’Azur in nearby France and I always find something wonderfully glamorous about driving along, especially in summer, with the glittering Mediterranean down below you fringed by the pine forests. (Obviously, that said, this is an experience that’s best enjoyed if you’re in the passenger seat as these roads aren’t often that wide so, needless to say, if you’re driving I’d definitely recommend keeping your eye on the road.)
The exception to the car idea however is Girona. Unless you’re using the city as a base for exploring the surrounding countryside and beaches, or are just visiting as part of a broader Costa Brava trip, Girona really is best seen either on foot or, if you really do want wheels, by bicycle.