As far as critical analysis goes I think the guy who paid for the film, producer Gustavo Alatriste, said it best: "I don't understand a thing in it. It's marvelous!" I agree. It's not a perfect film and it's not for everybody, but it is marvelous all the same. If you are into the finer side of Cinema then I recommend it. Or if you're into watching completely mindless garbage then there's always AX'EM.
As far as any symbolism goes this is what Bunuel himself had to say:
"I have not introduced a single symbol into the film, and those who hope for a thesis work from me, a work with a message, may keep on hoping! It is open to doubt whether EL ANGEL EXTERMINADOR is capable of interpretation. Everyone has the right to interpret it as he wishes. There are some who give it an interpretation that is solely erotico-sexual, others political. I would give it rather a historico-social interpretation. But when critics at the Cannes press conference asked Juan Luis why there is a bear in the film, wandering through the smart party, he answered, "Because my father likes bears." It's true. There are those who interpret the bear as the Soviet Union about to devour the bourgeoisie. That is nonsense. Then they asked him what was the meaning of the repetitions of shots in the film. I had anticipated this and told Juan Luis: "Answer that when I finished the film I decided it was still short, so to lengthen it..." People always want an explanation to everything. It is the consequence of centuries of bourgeois education. And for everything for which they cannot find an explanation, they resort in the last instance to God. But what is the use of that to them? Eventually they have to explain God."
Mic clearly visible. Also there's SIMON OF THE DESERT in the background.