I deal with both Atlantic Veneer and World Timber frequently. They both carry exotics, although World Timber has a larger selection. They do not have much in the way of American species, only curly maple, ambrosia maple, and holly I believe. Atlantic Veneer has quite a bit of American stuff, but they do not have the range of species in exotics that WT does. For example, I don't believe that they have wenge, ebony, cocobolo, East Indian rosewood, bubinga, etc.
If you want to go to World Timber, call first. Do not just show up there unannounced. If you call, ask for Matt, and tell him what you are interested in.
You do not need to call Atlantic Veneer ahead of time, but it would be worthwhile to call to get their hours. Sometimes they seem to close for an hour or two around lunch.
Hope this helps.
Matt