Vandalism and burglaries are not a big problem, but they do occur. Criminals know you are likely gone for a long while when you park at a trail head, so it is a concern. Be sure not to leave valuables in your car.
I have heard that some residents are unhappy about people coming into their community when we are all supposed to be following stay at home orders. Naturally, some people want to take advantage of the mountains and believe they can do so safely, so you can see both sides of the issue.
I don’t expect that residents are necessarily doing this as it could be anyone messing around.
Also keep in mind that they are also dealing with people illegally parking in areas that are CLEARLY posted and the Sheriff’s office is responding to residents when they call to complain about visitors parking on the road and blocking their driveways. Yucaipa PD posted on facebook about it today with outrageous images of vehicles parked right next to a No Parking Anytime sign. They issued several parking tickets today and will be a constant presence in Forest Falls and Angelus Oaks, so think before you park.