Once you leave the U.S. you will probably not be allowed to enter again until your green card is approved. You may not be able to get another Temporary Visitor Visa at the Embassy/Consulate in your country until your Green Card is Approved.
Plan carefully and be aware of what could happen while you are visiting or planning to visit the U.S. once a Green Card Application has been submitted for you.
Please contact a licensed Immigration attorney before you act on your specific situation. Immigration Laws and Federal Regulations are constantly changing and the general information provided can change over time.