Comfortable shoes and sandals you can walk in for a long time. You may spend several hours a day walking around, often at the beach.
Sunglasses, sunscreen, a sunhat, tank tops, swimming suit, water bottles. St. Pete can be a steam room.
Raingear. Expect thunderstorms.
Nice clothes, resume, clips, portfolio, and other job interview stuff. You may have a recruiting day, and lots of journalism bigwigs will be around Poynter, waiting for you to accost them.
A laptop is nice, and Poynter is setup for wireless networking. A car is also nice, but you'll be fine without one.
The sun sets beyond the Sunshine Bridge south of St. Petersburg.