AN ACR CREW MAY HAVE TAXIED ONTO A RWY WITHOUT CLRNC AT MMMX.

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ACR 1 FLT LANDED MMMX ON RWY 5R. WE EXITED RWY 5R; L ONTO TXWY E TO HOLD SHORT OF RWY 5L. TWR ON 118.1 CLRED TO CROSS RWY 5L AND CONTACT GND CTL ON 121.0. GND CLRED US ON TXWY B THEN INTO TXWY C THEN BACK TO TXWY B (THERE WERE MANY CONSTRUCTION AREAS ON THE RAMP). AS WE WERE ALMOST PAST B7; GND ASKED US TO MAKE A L TURN ONTO B7 AND THEN BACK-TAXI ON RWY 5L TO GET TO GATE X. WE MADE A VERY SHARP TURN ONTO B7. AS WE APCHED RWY 5L; THERE WAS AN ACR 2 SWBOUND (TAXIING) ON RWY 5L; JUST PAST E2. THERE WERE 2 ACR ACFT XING RWY 5L AT B3 (OFF TO OUR R). WE TURNED R ON RWY 5L AND PROCEEDED SW TO TXWY B6. WHEN WE WERE ALMOST TO B6; GND CTL SAID 'ACR 1; YOU WERE NOT CLRED ON THE RWY; YOU ARE NOW CLRED ON THE RWY; EXIT AT THE NEXT TXWY.' WE CONTINUED TO GATE X WITHOUT ANY PROBS. SINCE WE WERE THE ONLY ACFT THAT GND CTL WAS ISSUING INSTRUCTIONS TO IN ENGLISH; WE WERE NOT ABLE TO DETERMINE WHAT OTHER ACFT WERE BEING INSTRUCTED. THE DIFFICULTY IN UNDERSTANDING GND CTL'S ENGLISH AND THE BUSY FREQ (MOSTLY IN SPANISH) MADE THIS DIFFICULT AT BEST.