If you are going to go Everglades National Park, you don't need to buy a map. When you stop at the entrance to pay the fee ($10 per week) just ask for a map, they're free. The National Park Service has a really good map that shows all park roads and trails. It also shows the location of different habitats (pineland, cypress, sawgrass, freshwater marl prarie, hardwood hammock...). This map can also be accessed online as a pdf file from the Everglades National Park's website.
I don't know the rule regarding bikes on the main park road but I've seen people riding there before. Be advised that it is just a two lane road with cars driving in excess of 60 mph. As jodscrovy said, watersnakes (all 3 species) and frogs are everywhere, including all of the roads. Cottonmouths, garters, ribbons, and racers are also very common. You could find just about any species that resides within South Florida within the Park. Good luck...
-Joe