Just like people, cats seem to vary widely. One cat I had until a few years ago was VERY vocal, especially when I returned home or she came back in the house from a long ramble. I only had to give a little "brrrrp" to her, and she'd set off on a long tale, telling me everything that had been going on.
My present cat is very much the silent type. He speaks occasionally, usually when excited over food, but otherwise remains quite quiet. He can still make his wishes known very distinctly though: I know the exact looks and positions he adopts for "I'm hungry" or "I want to sit on your lap."
There is a small book titled "How To Talk To Your Cat," by Patricia Moyles which you might find interesting. A local library might be able to get hold of a copy.
-Paul