Go to maps.yahoo.com and type in
TPA in the address field
Tampa airport will appear.
Now click on the From This Location link.
TPA will be on the left side of the screen.
In the right side of the screen, type in
4000 E Busch Blvd
Tampa FL
Press get map and you have directions.
To make sure, print the maps. Start at TPA, and follow the roads to see how they go. When you are in the car, things can get confusing. It's about half an hour to the park.
Their web site also has directions here.
http://www.buschgardens.com/buschgardens/fla/pi_directions.aspx
You get park tickets at the park. Besides soda can discounts, there really aren't any other ways to get discounts. And the soda can discounts are only aired in Tampa on the radio, so I don't know if they are running. You may find discounts in the hotel lobby racks for a few bucks off.
No, they don't do anything special for B-days that I know of. Unless you visit a restaurant and make some kind of special reservations, but I don't know about it. Try to get there at 08:00am, go in early and beat the crowd.