A B737-300 DEPARTING MEXICO CITY HAS A POTENTIAL CONFLICT WITH A FOREIGN ACR ON THE SAME DEP PROC. THE PRECEDING B727 HAD MADE A DELAYED; WIDER TURN AT THE DEP FIX WHICH BROUGHT THE 2 ACFT CLOSER THAN ATC HAD PLANNED.

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FOREIGN ACR FLT Y; A BOEING 727; WAS CLRED FOR TKOF; RWY 23R. SEVERAL MINS LATER WE WERE CLRED FOR TKOF; RWY 23L. THE PINOS 2 DEP REQUIRES A L TURN AT (MW) TO JOIN THE DEP. WE WERE UNAWARE Y WAS SUPPOSED TO BE FLYING THE SAME DEP. IT APPEARED TO US HE OVERFLEW THE DEP AND WAS FLYING THE MEVIL ONE DEP. WE LOST SIGHT OF ACFT Y BECAUSE OF THE SUN IN OUR EYES. WE STARTED OUR TURN AT MW ON TIME AND SPD. AS WE CONTINUED OUR TURN SBOUND ACFT Y CAME INTO VIEW. SINCE OUR CLB RATE WAS HIGHER AND SPD SLOWER WE ACTUALLY TURNED INSIDE Y WHO APPEARED TO BE MAKING A VERY WIDE AND SHALLOW TURN. I ASKED THAT DEP CTLR IF Y WAS FLYING THE SAME DEP. DUE TO THE CTLR'S USE OF SPANISH AND THEN SWITCHING TO ENGLISH; I WAS NOT ABLE TO UNDERSTAND HIS FIRST XMISSION. ABOUT THE TIME I WAS TRYING TO ASK AGAIN; WE GOT THE TCASII RA TO DSND WHICH WE DID AND NO FURTHER ACTION WAS REQUIRED. THE CTLR THEN PROVIDED HEADING AND ALT TO REJOIN THE DEP. PROBABLE CAUSES: SUN IN EYES FOR TKOF AND DEP; MEXICAN CTLRS CONTINUOUS USE OF SPANISH WHEN SPEAKING WITH LCL CARRIERS. ENGLISH SPEAKING CREWS NEVER KNOW WHAT THEY ARE SAYING; LANGUAGE BARRIER AND DIFFERENT ACFT PERFORMANCE BTWN B737 AND B727.