You're going to have to purchase Microsoft Train Simulator for $50 at your local computure store (Best Buy, Staples, etc.). The software will come with six default routes: 2 in the US, 2 in Asia, and 2 in Europe. Now, to expand your virtual empire you want to go to www.train-sim.com. Hundreds of volunteers work long hours to build euqipment and routes of all shapes and sizes for free.
Currently there are only two Florida routes. The first one is the CSX-SCL A-Line from Tampa to Benson Jct. The second one is the CSX Florida Funnel from Jacksonville to Folkston, then to Waycross, GA. There is another route in the works which will be the FEC up to Jacksonville. The main goal for this group of people is to make a Florida empire.
As for Amtrak equipment I suggest dowloading the P-32, P-40, P-42 Genesis series locomotive set, the Superliner set, and then some baggage/mail/express. There's also a F-40, E-60CP, modifeid Acela Express, and much more.
Hope this helps. If you have any more questions do not hesitate to ask. B)