You could walk it though it is a bit complicated, much like getting around Pittsburgh in general. I'm guessing roughly it would take you 20 minutes to a half hour.
Walking out of the Omni, hang a left and then a quick right, then a left onto Smithfield (where the Kaufmann's clock is).
Follow Smithfield across the Smithfield Street Bridge. Turn right into Station Square (just before the Carson Street intersection).
(Stop right here...if you want you can proceed straight and you will see the Monongahela Incline across Carson Street. The view is slightly different-both are worth going on. )
Now, to proceed to the Duquesne Incline...
You'll pass Buca DiBeppo and the Sheraton on your right, then start walking through a parking lot, past the Gateway Clipper Fleet entrance.
At the end of the lot, when you come to the back of the Chevy Amphitheater, veer left and begin following the path along the amphitheater. (Be careful as cars use this road.) Just walk along this road, you'll go under the Fort Pitt Bridge, then eventually you will come to the parking lot for the Duquesne Incline.
You will walk up a flight of steps, then cross an overpass to the incline entrance.
If you should decide to drive, follow the same general directions, but turn right onto Carson Street and follow past the overpass, then take the first right into the parking lot. Hope you like it!