The municipality right outside of the national park is Jijoca. When you arrive in Jijoca you can find 4x4 vehicles shuttling people out to Jericoacoara for R$15. You cannot walk and there are not so many private cars going out, but you may be able to follow the trucks toward the park and look for a lift. There may be a bus for cheaper, though this is the most available means to reach the park.
Hitchhiking out - East toward Barreirinhas or West toward Fortaleza
When you take a 4x4 vehicle out of Jericoacoara, tell the driver you would like to go to the motorway roundabout to auto stop. It's the same roundabout for either direction. Cars are going a bit fast, so make sure to bring a large sign and make yourself visible. There is not shade, so better to start early if you can.
Accommodation and Sleep
There is plenty of space to wild camp along the giant hills that lead to the Pedra Furada famous touristic rock formation. Along the walk you can find your way down to some isolated beaches and a large cave possibly suitable for a tent.
There is a centrally located camping site called Camping Naturaleza that costs $5 USD per night, with a kitchen, fridge, bathrooms facilities, electricity, drinkable water, and the occasional donated fruit from local markets. It is a known spot for traveling street performers, musicians, jugglers, and artisans, and is characterized by an alternative culture.