score:3
The Footprint travel guide site has a good page about the park in English.
They describe how to get to the park independently and also mention a camp ground within the park at Los Fierros.
I did not quote the relevant parts here, as I am not sure about the copyright implications.
I think if there is a road in Bolivia, you can also park there. They are not as strict about this as other countries. Of course this is not an official answer.