Boondocking on the beach in Texas
I too have been to SPI many times, it is as safe as can be.
Just be careful, as you should be in any popular tourist area and you'll be fine. I spend my winters in the area, go to border towns in Mexico often, use common sense and have never had issues, yet many, very many worry about crime there. These folks sadly, often go nowhere for fear of the unknown, assuming the worse of people. Their loss.