For adoption, I recommend sets of the same sex, such as 0,3 or 3,0, kept in seperate roomy cages with stuff they can climb, until their owner can find out which ones get along well together. True sexed pairs would only result in fertile eggs, and some people would incubate them out of curiosity, even many times over a five year oeriod. Then, the only solution would be to release them, unless the peson is willing to advertise at Kingsnake and go to the trouble of of getting his babies weaned onto 3/4 inch crickets, 3/8's at least. That might necessitate de-worming and/or oral antibiotics. Few wild hatchlings make it to adulthood.
An owner can easily avoid fertile egging by having his/her females spayed. Then I would imagine they could be kept in groups of 1,2 or 1,3 in extremely roomy cages. But even so, wild adults have a higher risk of unprovoked attacks on cage-metes and unwary human fingers. The other way to get rid of firtile eggs is to let them be laid, and then freezing them. But I'm talking about hobby-parents of fertile eggs who want to raise clutches.
My recommendation for population control (as the regulars here already know) has always been a proven sharpshooter peace officer with a chocked .410 shotgun (the smallest shotgun). What would it be like as a wild iguana suddenly confind to jail for the rest of his/her life, for the amusement for human beings. Super-stress! I know my opinion is way politically incorrect, but it's the most expedient solution, and would cause the least suffering. Consider the slow death of an improperly cared-for captive iguana - that goes double for a WC adult iguana.
Roger