I would find a place to park at the Waterfront. I have been told that you can park in the lot of the hotel that’s near Costco, and I’ve parked there overnight without a problem.
As for the Glenwood Bridge area, on the weekends I do see people parking outside the scrapyard, and around the corner, under the overpass that runs beside that industrial building. But I would be surprised if that is truly public parking, and I assume that people get away with it because the scrapyard is closed on the weekend. I would ask the guy running the scale at the scrapyard before parking around there during the week.
I guess you could park on a side street in Hazelwood, but then you’d have to ride down Second Avenue, at least until the trail through ALMONO opens. But I wouldn’t leave a car that’s worth anything in lower Hazelwood all day, and I’ve never wanted to find out how badly rush-hour drivers would treat a bicyclist on Second Avenue between Hazelwood and Greenfield.
There is a Port Authority park and ride lot in Duquesne. It might be further than where your coworker is coming from, but the lot is right across 885 from the trail. From there, it’s 13 miles into town, most of it on the trail. Parking is free, and your coworker could always take a bus back if the weather turns nasty.