B727 CREW EXPERIENCED GPWS DURING APCH TO TLC.

Narrative

AFTER XING INTO MEXICAN AIRSPACE; IT APPEARED WE HAD TO REPEAT OUR CLRNCS TO ENSURE WE WERE COMPLYING. APPROX 40N MI OUT FROM TOULUCA; MEXICO; WE RECEIVED A DSCNT FROM FL210 TO 13000 FT. THE CAPT HAD BRIEFED THE ARR AND APCH. WE WERE EXPECTING TO ARC N AND LINE UP FOR THE ILS TO RWY 15. CAPT INITIATED CONTACT WITH APCH; WITH NO RESPONSE. HE WENT BACK TO PREVIOUS FREQ. THEY ADVISED US TO TRY AGAIN. THIS TIME WE RECEIVED A FAINT AND BARELY READABLE XMISSION. APCH; AT 15 DME; GAVE US A CLRNC TO DO THE VOR/DME TO RWY 15 AND ALIGN OURSELVES UP FOR THE STRAIGHT-IN TO RWY 15. THE CAPT REPEATED THE CLRNC; CONFIRMING WE WERE TO ARC TO VOR/DME APCH TO LINE UP TO RWY 15. THERE WAS NO RESPONSE. THE FO CONFIRMED THE R TURN WITH THE CAPT; IN WHICH HE SAID; I BELIEVE THIS IS CORRECT. WHILE IN THE TURN; THE CAPT ONCE AGAIN CALLED APCH TO CONFIRM THE CLRNC AND PROC WE WERE DOING. THE TURN TOOK APPROX 15-20 SECONDS. ROLLING OUT ON A DOWNWIND HDG; THE GPWS TERRAIN WARNING WENT OFF. THE FO SLIGHTLY HESITATED WHILE THE CAPT CAME ON THE CTLS AND INITIATED THE ESCAPE MANEUVER. AFTER CLBING APPROX 500-700 FT; THE MANEUVER WAS TERMINATED; AND WE FINALLY HEARD FROM APCH REQUESTING OUR HDG. THEY GAVE US A 210 DEG HDG TO INTERCEPT FINAL. EVERYTHING FROM THAT POINT ON WAS NORMAL.