Lis pendens is the first step in the foreclosure process. You can sell the house at any time up to the point where the court issues the final judgment, but you have to CLOSE by then - it cannot be just under contract. If your situation requires a short sale, then you should start that process as SOON as possible. Do NOT avoid speaking with your lender; engage them up front in the discussion. Government programs are incenting banks to be more cooperative in this process. In some cases, they will refer you to a Realtor who can list your house.
South Florida is becoming the short sale fraud capital of the universe, so you need to be EXTREMELY careful about who you choose to represent you. You need to find a Realtor familiar with the short sale process and preferablly one who does NOT do the negotiation themselves, instead using a third-party company with the expertise to negotiate. You should incur NO COST for the short sale, although you should engage an attorney to answer the foreclosure suit to avoid summary judgement.

The owner of the property is the owner of the property till somebody buys the property at the auction or till the property goes back to the bank. Till then, owner can sell the house, including when it is in lis pendens. If somebody presents the offer that is lower than the loan amount, the seller (or real estate agent) should contact the bank and check if they would accept less than what is owed on the property (short sale). If it is not checked with the bank, the seller should come up with the difference in the amount at the closing.

I hope this helps.