It would appear that your opinion is very much disputed. There are two distinct camps on this subject. One accepts the principals that animals can communicate through various ways including signs and noise. The other does not think that animals are capable of such things because God designed them that way. Evolution is still being disputed. If you believe in evolution, and the facts are pretty unquestionable, then it is only a tiny step to get to animals speaking either vocally or by using signs.
Interesting to note that most people who dispute the evidence that animals have intelligence are doing so from a religious dogma POV. Here is a link giving some evidence of what animals can do.

http://www.pigeon.psy.tufts.edu/psych26/language.htm

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055