My suggestion would be call the listing agent and ask what the status of the short sale is. Ask if the BPO has been done.. ask if they have excepted the offer that has been submitted.. if the offer has not been excepted usually they will still take offers.. In Florida some agents hold offers and submit a bunch together, some agents submit one at a time. Also it depends on the bank and the negotiator... Your best bet is really to call the listing agent and see what the status is of the existing offer then you will know where you stand.
Feel free to call me if I can ever help you look for a real estate need in Florida.