I signed a lease today and afterwards I regreted the decision. I talked with the neighbors and they told me a horror story. I really want to get out! NOW! I'm in FL and I have heard something about opting out of a contract within 24 or 48 hours. Anybody... please help, QUICK!

No, unless the lease had a release clause in it, ( most don't) you are stuck in the lease, and Florida is the worst state in the US, since they don't even require the landlord to try and rent out the apartment, they can merely hold you liable even if you don't move in.
YOu need to go talk to them and see if they will let you out if they just keep all the money you have given them, if you need out badly