Some better than others, both on an individual and a species level. I let a personal issue creep into my writing. Amazons and Greys, more than most other parrots, seem to use talking as their calling card probably because, while they are gorgeous birds, they don't have the flash of many cockatoos or macaws. However, once in the home, bonded, comfortable and appreciated for who they are, most people don't really care if their 'Zon ever speaks. Not anything that I understood, anyway.
Amazons communicate clearly.
Amazons, slightly more than macaws and MUCH more than cockatoos, are clear and direct in their messages. Amazons are very straight-ahead birds. They are a behaviorist's dream. This isn't because they don't have problems. We as owners, breeders and whomever can and do turn our amazons into screamers, biters, pluckers and spouse haters all the time, but there's a difference in working with the greenies.