B727-200 CARGO CREW RPTS NEAR MISS AT SJO.

Narrative

WE WERE A B757 CARGO WITH 2 PAX (JUMP SEAT) LNDG SJO COSTA RICA FROM MIA. WE WERE CLRED FOR THE ILS RWY 7 AT SJO WITH COCO APCH. WE WERE SWITCHED TO TWR AT 11 NM. COCO TWR ASKED US TO RPT A 3 NM FINAL. TWR CLRED A PIPER NAVAJO INTO POS (RWY 7) AND HE WAS IN SIGHT. AT 4200 FT MSL (1200 FT AGL) I SPOTTED TFC AT 12:30 - 1 O'CLOCK POS COMING OPPOSITE DIRECTION. I QUICKLY LEVELED OFF AND SLIGHTLY STARTED TURNING L WHEN I ANALYZED THE CESSNA CARAVAN WAS GOING TO PASS TO THE R. HE WAS AT 4000 FT; 500 FT TO THE R. AFTER LNDG WE TOLD TWR ABOUT IT. TWR SAID APCH AND HIM TOLD US ABOUT IT. TWR ADMITTED TO US WE NEVER ACKNOWLEDGED; BUT HE WAS BUSY AND HAD TO CLR THE NAVAJO FOR TKOF. WE NEVER HEARD HIM TALKING TO THE C208 CARAVAN AND ASSUME WE CROSSED EACH OTHER WHEN GOING TO TWR AND HIM TO DEP. WE HAVE NO TCASII BECAUSE IT'S NOT REQUIRED BY THE FAA FOR CARGO ACFT. FLYING OVERSEAS; SOME OF THE ATC CLRNCS IN SPANISH FOR THE LCL TFC; CUT DOWN THE SITUATIONAL AWARENESS PICTURE. IT'S CRIMINAL NOT TO HAVE TCASII MANDATED; AND THE LACK OF IT WAS A CONTRIBUTING FACTOR.