I think one of the joys of this short story is that it defies interpretation. You need to note how the villagers are often exposed as foolish and gullible in their beliefs, and also how they try to make sense of the world. They stick fast to "facts" even though they are clearly ridiculous, such as the fact that angels eat mothballs, and they jump to impossible conclusions, for example when some argue that the old man should be proclaimed "mayor of the world." It is almost as if once they have conceived of an idea they make reality "fit" to support that idea despite any protestations to the contrary - or until a "better" version of the "truth" comes along and then the process beings again. Of course, the villagers, although they can be said to be figures of fun in this sense, contain many characteristics which we can identify whatever our time or culture - for example the unquestioning belief in their own wisdom and their stubborn clinging to their own ideas are aspects which we can all identify.
It is clear though that while there are a few hints into this story as to the "meaning" or "allegory" there are no conclusive pointers that give one definitive explanation. We are left, much like the villagers therefore, to try and make some sort of meaning from these strange and bizarre events. The last laugh seems to be with Marquez, however, as we prove ourselves to be like the villagers trying to make sense of this story and coming up with very different and ridiculous answers. Therefore, if there is a "meaning", it is that there is no "meaning" - it is more about the process by which we make "meaning" and how we support our conclusions.
One example of possible irony is that when they found out the man was a supposed angel, they treated him as if he was no better than a dog.
Another possible example of irony is at the end, where Elisenda sighs in relief when the angel leaves, even though it was all because of the angel that the villagers became wealthy.
The reader expects the villagers to be grateful towards the angel because he indirectly causes them to become wealthy, but instead they look upon him as though he was a burden.
Angels are commonly thought of to be elegant, beautiful creatures usually wearing white with a spiritual presence, not disease infested beings who wallow in their own filth. This allegory makes you question your own perception of what angels look like. We do not know for sure that all angles are not old men with few teeth who reek of squalor. The townspeople try, of course, to put this "angel in their own Biblical context. "The priest tested the man by speaking to him in Latin, the language of God, and by looking for a miracle". It is ironic because the old man is not treated as an angel or even an allegorical angel. The old man is treated as a sideshow, a chance for the couple to sell tickets to an absurd spectacle. In the end Marquez asks how might we treat the divine should it not conform to our "mythic picture"?