It's possible to leave your car on parking during the time of your walk.
On free parking, you have 2 possibilities :
These parkings are free, but not watched. However, and for more safety, you can inform the police station by giving them the following information : name and first name of the owner of the car, a copy of the car documents and your trip dates. Police station of St Jean Pied de Port : + 33 188.8.131.52.10
On paying parking, you have also 2 possibilities :