I’ll be arriving by Amtrak on a Thursday night, and beginning my ride on a Friday morning, as early as I can manage to get myself awake and ready to roll (train gets to Pittsburgh at midnight). Everybody makes a big deal that the mile from the city to Homestead is too dangerous to ride, but I can’t imagine that it’s too tricky.
The ‘official’ route is on a two-lane road that typically sees speeds upwards of 50 mph outside of rush hour. However, if you’re okay with riding or walking a few dozen yards on railroad stone, there’s an alternative that involves very little paved road. Somewhere on here someone posted a map of how to get to & through it, but I can’t find it ATM.
(ETA: basically, you’ll want to take the Eliza Furnace Trail from Downtown about 2.5mi upriver, then cross to the South Side Trail. Continue upriver another couple miles until the trail ends. There’s a path down the railroad tracks, through a couple of private (but not terribly concerned) properties, and around the edges of Sandcastle amusement park, then through the Waterfront at Homestead shopping center to the trailhead.)
I could offer being a guide from the start in Downtown (The Point), to the Steel Valley Trail in Homestead. From there-on the path is pretty direct.
I would take the Jail Trail, Hot Metal Bridge to the Southside Trail, the bit of gravel path by train tracks on Greenfield, on to Sandcastle parking lot, the Waterfront and on-to Pump House/Steel Valley trail.
Ok, to be a contrarian, I am surprised that on one was suggested: Eliza Furnace Trail to new Hazelwood Trail. Short distance on Second Avenue. Hop RR tracks at structure for Glenwwod Bridge. Follow extended Duck Hollow Trail to Homestead Greys/High Level Bridge. Sidewalk to Waterfront ramps. Pick up trail there.