ya. you can leave U.S as long as you receive your GC. If you leave the U.S for more than one year otherwise you will break you GC status. You can leave the U.S for a maximum period of 2 years with an Application for Travel Document from the USCIS.
If you leave the U.S for more than one year without USCIS approval, you will lose your status for sure!!.
Take care!
Thanks,