COMMUTER TAXIES TO WRONG RWY.

Narrative

OUR ACFT HAD LANDED AT PBI APPROX 20 MINS EARLIER ON RWY 9L. I HAD OBTAINED ATIS INFO AND SPECIFIED RWY 9L. WHEN TAXIING OUT; APPARENTLY; ONE CTLR WAS HANDLING ALL POS. THERE WAS SOME CONFUSION OVER TRIP NUMBERS WHICH WAS STRAIGHTENED OUT AND WE THEN HEARD 'CLRED TO TAXI...' THE END OF WHICH WAS GARBLED AND INDISTINCT AS THE CTLR SEEMED TO TURN HEAD AWAY FROM MICROPHONE. HAVING HEARD THE TAXI CLRNC AND ANTICIPATING RWY 9L; I CONTINUED FOR IT. WE HAD ACCOMPLISHED OUR CHKLISTS AND TAXIED FOR SEVERAL MINS WHEN GND CALLED. AT THAT POINT; HE ADVISED US HE HAD CLRED US TO TAXI TO RWY 13. WE HAD CROSSED 13-31 ENRTE TO 9L. I DON'T KNOW IF HE DID OR NOT BECAUSE OF THE CONFUSION LEAVING THE RAMP. I WAS; HOWEVER; LOCKED IN ON 9L. OBVIOUSLY; THERE WERE A NUMBER OF FACTORS: CONFUSION LEAVING RAMP. 1 CTLR WORKING ALL POS (I BELIEVE). LACK OF CLR COM. INACTIVITY ON ACFT LEADING TO RELAXED ATMOSPHERE. WE WERE ALREADY 2000-3000 FT PAST 13 BEFORE GND REALIZED WHERE WE WERE LOCATED. PREVIOUS OPS AND ATIS WERE RELIED ON AND WERE INACCURATE. I HAVE ALWAYS MADE IT A HABIT TO QUESTION ANYTHING THAT I WAS NOT CLR ON. IN THIS CASE; I HAD NO DOUBT IN MY MIND THAT I WAS CLRED TO 9L. I STILL DON'T KNOW THAT I WASN'T AND THIS WAS A CTLR ERROR DUE TO THE BAD COM. JUST AS A NOTE; WE CAREFULLY CHKED TFC PRIOR TO XING 13-31.