B737-700 FLT CREW IS VECTORED FOR AN APCH TO A DIFFERENT RWY; ENCOUNTERS AN OBSTACLE; TAKES EVASIVE ACTION AND LANDS.

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ATIS INDICATED RWY 10 IN USE FOR ARRS. CLRED 'DIRECT COLUMN; DSND TO 2000 FT AND JOIN THE LOC 10; EXPECT A VISUAL TO RWY 10.' JUST A FEW MI (MAYBE 3) OUTSIDE OF COLUMN WE GET SOMETHING TO THE EFFECT OF 'COMPANY; TURN L 20 DEGS; WE ARE VECTORING YOU OUT FOR A VISUAL TO RWY 15R AS WE HAVE A DEP OFF RWY 28 WE NEED TO GET OUT.' WE SCRAMBLED TO GET READY FOR RWY 15R AS IT CAUGHT US OFF GUARD. (NO VASI; BUT AT LEAST IT HAS AN ILS; RIGHT?) AT THIS POINT WE COULD STILL SEE THE FIELD BUT WE HADN'T CALLED IT YET. WE WERE LEVEL AT 2000 FT AS ASSIGNED. THEN; 'COMPANY; TURN L HDG 030 DEGS.' AS THE ARPT STARTS LEAVING VISUAL RANGE; I BEGAN TO GET CONCERNED ABOUT LEAVING CLASS B AIRSPACE. A COUPLE OF 'CHART FUMBLES' LATER AND I REALIZE THE LIMIT FOR US WOULD BE 12 FROM BAL. AS I AM ABOUT TO SQUAWK IT WE GET OUR BASE TURN KEEPING US AROUND 11 FROM BAL. 'COMPANY; DO YOU HAVE THE FIELD?' I'M THINKING 'WE DID WHEN WE WERE LINED UP WITH RWY 10; OR WHEN WE WERE ON A 5 MI DOWNWIND FOR RWY 15R.' AFTER A BRIEF SEARCH/DISCUSSION IN THE COCKPIT; WE CALLED THE FIELD. AS WE TURNED FINAL; THE FIELD WASN'T THE ONLY THING WE COULD SEE. TOO BAD ATC HADN'T ASKED US IF WE COULD ALSO SEE THE 1503 FT TOWERS WE WERE HEADED STRAIGHT IN FOR ABOUT 2-3 MI. MY FO MADE A TURN SO AS TO KEEP THE TOWERS IN SIGHT AND PROVIDE SAFE LATERAL CLRNC TO MAKE UP FOR OUR LACKLUSTER VERT CLRNC. WE HAD FAILED TO BRIEF THE TOWERS IN OUR HURRIED AND UNEXPECTED CHANGE TO RWY 15R. (MSA WAS 2600 FT; AND THAT ILS SEGMENT WOULD HAVE PUT US AT 2500 FT.) THEN; 'COMPANY; YOU PROBABLY WON'T GET ANY ILS OR GS SIGNAL; THE LOC IS PROBABLY STILL TURNED AROUND.' YEAH; WE NOTICED. IN SUMMARY; WE WERE ASSIGNED AN ALT AND LAST MIN RADAR VECTOR TAKING US AWAY FROM OUR PLANNED RWY. THEN WE WERE FLOWN TO THE EDGE OF CLASS B AIRSPACE UNTIL WE CALLED THE FIELD; AT WHICH POINT WE HAD TO PERFORM MANEUVERING TO ENSURE PROPER OBSTACLE CLRNC FOLLOWED BY A NIGHT LNDG TO A RWY WITH NO VERT GUIDANCE. WHY? OF COURSE WE SHOULD HAVE CAUGHT SOME THINGS SOONER OURSELVES; BUT DELAYING A DEP TO AVOID THE ABOVE SEEMS PRUDENT.