In the early 2000s many Russians acquired villas around Costa Brava, inflating restaurant prices, and bringing many expensive cars to the region.
The main airport is in Girona which is the destination for Ryanair, transavia.com and Wizzair. Alternatively, you can fly into Barcelona's El Prat airport. Girona can also be reached by train.
If you want to explore a lot of the coastal cities then renting a car is your best option. There is regual bus service between the towns but nothing compares driving along and stopping where you like.
The unknown gem of the Costa Brava is Tossa de Mar. This beautiful little fishing village is one of the least developed on the northern Spanish Mediterranean coast. Tossa is still a fishermen's town, with the quaint very-narrow cobblestoned streets, white houses, and beautiful coastline. Tossa also boasts some very well-preserved medieval ruins -- including walls and towers which protected the town between the thirteenth and sixteenth centuries.
If you like casinos and more luxurious accommodations, go to Lloret de Mar. However, if you prefer the less developed beaches, and don't mind less ostentatious accommodations, Tossa de Mar is for you.
There are scuba diving outings to the "Illes Medes" (Medes Islands) National Reserve Park from L'Estartit. Cadaques also has various dive shops to explore the area.