The lizards in the hotel lounge that Raoul Duke sees are symbolic of the quote in the beginning of the movie.  The quote is by Dr. Johnson and goes as follows:  “He who makes a beast of himself gets rid of the pain of being a man.”  What I interpreted this quote to mean is that beasts are dumb and have very little to worry about as opposed to human beings.  This is the typical idea that human society shares.  With that said the lizards in the lounge were just that.  They were seen as dumb beasts with little worries and indulging in their pleasures.  This ties in with drugs, because at the time drugs were viewed as uncivilized and for those who are counterproductive in our society.  So basically anyone who did drugs and drank would be viewed as a misfit or degenerate to society.  Based on accounts of people who took some forms of drugs, it is suggested that when one is hallucinating or even dreaming, they see things they wouldn’t normally see ( in this case humanoid lizards).  These are usually symbolic of something, in this case being that Duke’s hallucination shows him the beasts that are no longer man and indulge in simple pleasures.  Therefore, Duke thinks that people who do these types of recreational activities are not in the brightest of spotlights within our society.