Travellers mix: majority are French; some Italians.
There's no direct train connection to Cadaqués, but you can make the first part of your ride by train. From Barcelona, one way to reach Cadaques is by train from the Plaza Catalunya, at the center of the city on the west point of Las Ramblas. From here, hop on a train heading North to Figueres, a journey that should last about an hour and a half. From the Figueres train station, walk straight out into the city and you'll see the bus station on your left. From here, you can hop on a bus to Cadaques(which leave frequently), where you'll take an hour long journey up through the Catalonia hills and at last down into the beautiful sleepy town of Cadaques.
The company Sarfa  operates a daily service direct from Barcelona to Cadaques. The timetable changes depending on the season. The buses leave from the North Station which is close to "Arc de Triomf" (and metro station) and is also within walking distance from the centre of the city (about 35 minutes walk). Beware holidays! The timetable is reduced considerably and you might have to wait 7 hours between the busses, especially if you want to leave Cadaqués and catch a plane... In this case you can take a taxi to Rosas and hop there on one of the more frequent buses.
It is possible to catch a ferry from the nearby town of Roses. During much of the year these ferries travel several times a day.
Because of the geography surrounding the town of Cadaques, the traditional way for the townpeople to travel was walking, by boat (rowing or sailing) or by "Tartana". It is still possible (and enjoyable) to walk to Cadaques either from Roses or Port de la Selva. From Roses there is a marked trail which follows the coast. The walk is approximately 15 kilometers and passes several bays and beaches on the way. The walk is marked with small red and white painted marks which are located on rocks and signs.
Arriving by car is quite easy; there are several free parkings in the city. One of them is left side from the downtown when you arrive by car, close to the beach (open 9am-8pm).
The city structure of Cadaques is short and sweet, where shiny tiles lead travellers all through the city, from the bars and cantinas at the city center beachfront, to the hotels and private homes on the surrounding sides of the Cap de Creus peninsula. You can pretty much walk everywhere you want, but renting a vespa is nice option to explore the surrounding countryside.
Fish restaurants of Cadaques are highly rated in the region.