Eagle Creek is a very busy parking area over the weekend. On a busy weekend ther might be a risk of somebody popping a windshield to get some coins or a wallet but I don't know if thy would risk sawing off a cat. converter which would take a bit more time and would draw more attention. Admittedly there is risk and I agree with stevefrom dodge that it is not worse than any other. Just don't leave anything to invite temptation.
I have noticed that the thread regarding trailhead breakins has been very active and has covered many nearby areas. Unfortunately, the threat is there, but I think the series of postings make things sound a bit worse than they are.
Don't be afraid just use common sense.
“We must go beyond textbooks, go out into the bypaths and untrodden depths of the wilderness and travel and explore and tell the world the glories of our journey.”
~John Hope Franklin