People have always been getting their shit stolen at glamis. I've never locked anything up at my camp. Then again, our camp is about 15-20 MoHo's or toyhaulers. As far as "gangs" go, I doubt that gang bangers are out to jack your 1997 kx 125, so they can part it out, and make a few bucks.
As dumb as gang members are, they're not really in the business of parting out RV's, or bikes. I've never heard of a "problem" though. There's always trouble makers everywhere you go, but 99.999% of the people that are there are there to have a good time. I've been going to glamis since I was about 6 months old, and honestly, the only thing I've noticed changing, is there are more people out there in general, which means there will be more people up to no good. Most of the thefts are of coolers, or bbq's. I have a few buddies that work for BLM, and they usually only have one or two theft reports a weekend. Which isn't too bad, considering on a busy weekend you could have over 200,000 people out there.
I wouldn't be worried. If your bikes aren't insured, just lock them up. If you're really worried, keep your coolers and bbq's in your trailer, and you'll be good. We leave camp sometimes for 6-8 hours, and never once have I worried that my things were going to get stolen.