B737-900 FLT CREW ENCOUNTERS LLWS AT 500 FEET AGL ON APPROACH TO PSP AND CONTINUES TO LAND WITH FLAPS RETRACTED TO 30 DEGREES.

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LOTS OF VECTORING INTO PSP (VARIOUS OTHER ACFT); WE HAD AN 8 MI; MID-FIELD 45 DEG L DOWNWIND ENTRY FOR A VISUAL INTO RWY 13. HAD REQUESTED/BRIEFED AND SET UP FOR AN PNP TO RWY 13; BUT DUE TO TFC...THE WIND WAS (FROM TWR VARIOUS DIRECTIONS/SPDS) RIGHT DOWN THE MOUNTAIN INTO OUR FACE TURNING FROM BASE TO FINAL. NO LLWS ALERT/FORECAST/NOR ON ATIS; SO WE WERE THE FIRST TO ENCOUNTER IT. IT HAPPENED AT 500 FT AGL AS I WAS AT +20 KIAS; SO I ELECTED TO SELECT FLAPS 30 DEGS AND CONTINUE TO LAND (ALREADY HAD +10/FLAPS 40 DEGS SELECTED FOR THE RNAV RWY 13). THE ONLY PROB (OTHER THAN THE BLOWBACK/IT WAS LOGGED AND MAINT MET THE ACFT) WAS A HOT BRAKE WHICH MAINT TOLD US ABOUT WHEN HE MET THE ACFT. BEEF UP THE B-900 FLAPS OR FIX THE HIGH LNDG SPDS AND BEEF UP THE BRAKES. BOTH SEEM TO BE ON THE WEAK SIDE OF SAFETY. THIS WOULD NOT HAVE BEEN A REPORTABLE EVENT IN THE OTHER B737'S. WITH THE ALREADY INFLATED B-900 LNDG SPDS THE (ALMOST) MANDATORY 40 DEG FLAP SELECTION FOR LNDG AN EVENT SUCH AS THIS IS A CERTAINTY! ANY WAY TO FIX THE PROB...GET STRONGER FLAPS; LOWER LNDG SPDS; ETC?