It's a problem all over. I manage a nature preserve with three trail heads and over the course of a year, there will be break-ins and vandalism in the parking lots. In state/national parks where there is a entrance fee and/or checkpoint, break-ins are rare.
Make sure you are fully insured. Crooks already know the goodies are in the trunk....so don't leave anything valuable in the car at all if possible.
Sometimes you can park at a local business and be shuttled to the trail head, and picked up when you are done. It's different everywhere, so your results may vary.