Welcome to the neighborhood!
I, too, commute in the flatlands of FL. I'm in Clearwater so it's really flat.
1. How long have you been riding your cruiser to work?
2. Is your fitness level to the point of moving up in speed?
3. Your budget can/will get you a good bike - but defining what you need and where you want to go with bikes and commuting will determine what is recommended.

I ride a cheap 7-speed Schwinn cruiser with a seat-post rack. But, I'm OLD and don't give a rip what people think of me! I can imagine you want something a little snazzier! I'm sure the gurus will be chiming in shortly!