there are a couple ways to go. the least traffic filled way is probably to cross the highland park bridge (on the downstream sidewalk), make a left toward sharpsburg then go under the 62nd st bridge toward the river and hop on the access rd next to the tracks. stay on that road and it will take you right into the riverfront park in millvale.
you could also follow the google directions and take the sidewalk on the upstream side of the 40th st bridge and wind up right in millvale.
if you want a really long but pleasant ride you could always take hampton/highland/elsworth(via the pedestrian bridge behind trek)/neville/boundary to junction hollow and then to the jail trail to the point and take the ft dusquene pedestrian bridge over to the northside and then take the trail out to millvale.
fyi, the trail along the north side of the river goes right under 28 but is very much separated. google isnt really trying to put you or your bike on the highway.