No need to worry about a store in Miami. ArtCraft Chemicals has everything ( chemistry wise ) that a photographer will likely need, and will ship directly to your door. Of course, Formulary also has a ready supply of chemicals for photographers. However, one suspects that shipping from Montana will be more costly than shipping from New York. Premixed chemicals are available from many vendors, but many on this coast use B&H or Adorama.....there are others that I am sure are equally as good.

http://www.artcraftchemicals.com/products/