Here are some tips, whether you already follow or not, for drying mangoes:
Cut all pieces the same thickness, approx. 1/4 inch
No need to soak/spray/treat in any solution
IF your dehydrator has a temp setting, dry at 120 degrees*
Drying time should take about 20-24 hours*
I just put in a ziploc bag (as it doesn't stay around that long) or you could use a food sealer if storing any length of time
* - I have found this to be optimal
I also dehydrate fresh bananas and sapodillas (thanks Harry & Murahilin)...they seem to take a little less time to dehydrate. While mango and bananas are yummy dehydrated, sapodilla is the best of the fruits I have dehydrated. tastes like brown sugar candy