I air dried 12/4 in PA and it was down to 10% within 2.5 years. Possibly 2 years. After the first 6 months of drying lumber, you kinda forget about it and stop tracking its moisture content. That is to say, your climate should absolutely dry those slabs in under two years. Im also guessing they are atleast 20%+ mc right now and i would definitely not want that wet wood getting baked by the sun whilst simultaneously experiencing 80mph winds. I am with the other guy, i would tarp it or have a plywood cover to block the sun.

Looks like interesting material, good luck on the transport!