If you come by train, take a ticket to Carcassonne.
From Carcassonne to Quillan you can travel further for only 1 Euro p.p. by TER train or by coach from the local railways company depending on the time of day. Ask for the special 1 euro ticket at the desk. Click here for an online search. (Or click here for the local timetable and choose line Carcassonne-Limoux-Quillan to see the pdf).
If you take the train to Perpignan, from there on the bus 100 will also take you to Quillan for 1 euro. Check if the hours are sufficiently good.
Important: book a taxi well in advance from Quillan station to L’Assaladou.
For approximately 29 Euro Taxi Jacky (00 33 (468) 20 01 92) will take you.
So a family of 4 pays about 33 euros for the entire local journey from Carcassonne onwards!
Tgv tickets can be booked at uk.voyages-sncf.com/en/ or simply at the counter of a (sufficiently large) train station.
The cheapest tickets are called ‘Prems’. They appear on the site 3 months before departure. (Or 4 months before departure in the summer period).