A PA31T PLT TAXIES ONTO RWY 27L AT PBI; THINKING THAT IT IS TXWY R.

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AFTER BEING PARKED OVERNIGHT AT FBO; I PREFLTED THE ACFT AND STARTED BOTH ENGS AND COMPLETED THE INSIDE CHKLIST UP TO ENG RUNUP. I THEN CALLED CLRNC DELIVERY TO PICK UP MY IFR. THEY WERE TELLING SEVERAL ACFT TO STAND BY. ALSO; ATIS WAS OFF THE AIR. I ASSUMED THE SAME PERSON WAS RECORDING A NEW ATIS. INSTEAD OF STAYING PARKED AND BURNING FUEL; I ELECTED TO CALL GND AND TAXI TO THE ACTIVE RWY. I COULD SEE THAT RWY 27R WAS BEING USED. SINCE I HAD NEVER BEEN TO THIS ARPT BEFORE; I ASKED THE GND CTLR FOR A PROGRESSIVE TAXI. THE GND CTLR INSTRUCTED ME TO TAXI STRAIGHT AHEAD TO TXWY R. I TAXIED STRAIGHT AHEAD AND ONTO WHAT I THOUGHT WAS TXWY R; BUT WAS IN FACT RWY 27L. I IMMEDIATELY TURNED BACK ONTO THE LARGE CONCRETE RAMP THAT MUST HAVE BEEN TXWY R AND CONTINUED MY TAXI TO RWY 27R. I DON'T KNOW IF RWY 27L WAS AN ACTIVE OR INACTIVE RWY AT THE TIME. THE GND CTLR JUST TOLD ME THAT I HAD MADE A WRONG TURN AND TO MAKE A 180 DEG TURN; WHICH I WAS ALREADY DOING WHEN HE CALLED. POINTS OF CONFUSION: THE TXWY SIGN SITS IN THE GRASS NEXT TO RWY 27L AND IT LOOKS LIKE THE CONCRETE ON THE OTHER SIDE OF THE GRASS IS THE TXWY. IT WOULD HELP IF THERE WAS AN ARROW ON THAT SIGN POINTING TO THE R. I DIDN'T NOTICE THE HOLD SHORT YELLOW LINES ON THE TXWY LEADING TO RWY 27L NOR DID I NOTICE A LARGE YELLOW LINE MARKING TXWY R. I SHOULD HAVE STUDIED THE ARPT LAYOUT DIAGRAM MORE CLOSELY INSTEAD OF RELYING ON THE GND CTLR SO MUCH.