You don't need lockers for sand. Just air your tires down and you will be fine. If you find yourself in a bind just put it in 4low and back out.

To be honest unless I am going out for a couple of days I don't even air down and have never been stuck in sand. I play in it in 2wd alot as well.

Although I did just two a blazer out of the soft deep stuff going into Orgen Inlet this week. He wasn't aired down though and I don't think ever drove on the beach.