It is quite safe from people. Leaving automobiles locked will be safe everywhere. Putting things out of sight of others will help ensure this. It is normal to ask others to watch your things even if you just met them, e.g. in a campground or on the beach.
The most risky thing is to leave any food or scraps, even garbage out. The bears will smell it and then tear up your campsite to find more. It is illegal to feed any animals at all, even if they are cute, for this reason. Also, never get too close to a deer or elk, which may run at you. Bear and other animal attacks are rare, and will not happen if you follow the instructions you will be given.
fees/permits
A national park pass or daily fee for entry applies. Special fishing licences are required. Camping permits are required, and so are fire permits within camp grounds. It is free to burn wood at picnic sites to cook your supper.