You should have a pretty good idea of your distance from the airport, via INS, DME, or FMS... Without those, how are you going to find the FAF if you do not have the appropriate VOR or NDB to triangulate your position?
If you are 500' high, and your normal rate of descent on the G/S is 800 FPM, and your max rate of descent is 2000 FPM down to 1000' AGL, you can get down to the GS in 25 seconds. At 150 KT, that would take just a little over a mile. At 1000' you are about 3.3 mi from touchdown, so you could technically do it from just under 5 mi (with a bit of slack for roundouts). If you intercept the LOC at 7 or 8 mi out (not unusual), there should be no problem making it down.
If you don't have DME, ATC should give you (or you should request) distance from the FAF when you intercept. You should then be able to make a decision to either continue or ask for another approach setup (or a delay vector).