It depends what you mean by preforeclosure....there are several stages in the process. Florida is a what is termed as a Judicial state. It has to go through the courts to foreclose. If you want to buy it while the process is playing out (no matter what motions have been filed) you will need the owner to cooperate with the bank (banks prefer engaging a realtor or an attorney because of the extensive paperwork) and it will go through a short sale process. If the owner does not cooperate, the bank will foreclose and hand it over to an asset management company.
In either case the bank will send an associate of some kind out to determine a price for the house. That price will generally reflect a market value less the cost of repairs. They don't leave a lot of cheese in the deal as far as I have seen. Now, if it is a value around 40k or below..cash buyers are snatching them up.
That said, if you have enough cash on hand and the owner is agreeable, the bank may accept a lesser cash offer early in the process in order to save substantial legal costs in foreclosure actions.