DH and I have done a lot of backcountry hiking/camping in Yellowstone NP We saw a lot of black and grizzly bears (some too close for comfort) I would not leave food in a car. Remember to cook away from the sleeping area as well. You can get some rope and hang it in a bag (stuff sac) from a tree (if there are any in the area) away from the campsite.

I would call the campground and ask them what people do. i would guess they have some type of community container for people to use.