Not sure about availability but I did read about crime in that area you might not be aware of. Read this in https://www.rvtravel.com/rvt-933b/ and thought you might like to know that there has been some crime issues there as well here is another site with specific info on boon docking there with respect to crime https://www.tripadvisor.ca/ShowTopic-g56691-i85-k11796521-Crime_In_South_Padre_Island-South_Padre_Island_Texas.html

Thanks for the links Randy.
I found these comments by local residents telling:

"Any popular resort area will have a relatively high crime rate. Throw loads of total strangers away from the eyes of their hometown and criminals who know visitors are on vacation and therefor careless, and you will have more crime. But SPI is safe. You can get your stuff stolen if you leave it unattended, just as if you left it unattended in a park at home. You can get your car broken into if you leave valuables in view, just like at home. If you decide to go in March, you can get mixed up with violent drunks, just like if you seek out the hard partying venues at home. Even more, because they will know no one will recognize them on a video."

"What you want instead is to know how safe people normally feel on SPI. That's a pretty good indicator of if the physical layout looks like it's not attractive to crime and if there's a law enforcement presence. But the regular tourist who takes sane precautions has little to worry about."

"We live on South Padre Island and know of very little crime except people playing their music too loud from golfcar rentals. We see very few speeders as police enforce the speed limit."

"Now Spring Break at the 2 concert areas is the exception. The rest of the Island is fine; we go out to eat, enjoy the beach and do our usual activities.That being said we do bring our young grandchildren to the beach at spring break and walk on the beach barefoot!
Much ado about nothing."

Now I want to know, where are the so-called "concert areas"? Are they on the actual beach boondocking areas? I would chose to give them a wide berth to say the least!

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.

Thanks for the tips and reassurance Geeky Guy.

You make an excellent point. We are almost through our first year at an RV park (in Canada) we've always wanted to camp at but were always told by friends that it was one of the worst campgrounds in the area. But it's been fine. Sure we've had people wander through our spot, but I think that is almost everywhere. Plus all the other fulltimers keep an eye out for each other. But as you say, if you don't venture out to at least try you never know what you are missing. Where's you sense of adventure! You have an RV for a reason. Use it!

SPI was a wonderful stop for us. Can't beat free beachfront camping. I felt safe and will certainly go back. No idea on the spring break scene but I personally wouldn't want to try and camp anywhere that would be a party spot.