Two questions: How far you are interested in biking, and how far are you interested in driving once you get off the major highway?
I live just off Perry Highway about halfway between Wexford and West View. IMHO anywhere south of me is OK and anyplace north inhospitable. Babcock Blvd is a nice, flat, reasonably unbusy road, unlike McKnight (busy) or Perry/Perrysville (hilly). Official P&R space is limited, though, and it's quite a ways off 279.
My hunch, though, is that doing a "hide-and-ride" in West View or Avalon/Bellevue might be your best bet.
Edit: From Babcock, wiggle through Millvale, then either MarylandAve/Rt28sidewalk/40thStBr or river trail to 31SB or 16SB, would do you well.