Sometimes the sexual difference don't present themselves unless both sexes are present. Males will show odontoides, but sometimes will only get full growth with females present. The females will be broader and fatter. All these cues are meaningless without another specimen of the opposite sex to compare to though. That's pretty much the norm for plecos. Maybe Charles will have other ideas.
I do find both females and males will use the caves in my tank, but like Charles mentioned, my matured females are visibly bigger, fatter, rounder than the males, and matured males are obviously hairier on the side of the gills and all over the body. Hope this helps!