Yes. From 21st street and other numbered streets - up to 24? - one can access the river trail in the strip. From the strip, the trail ramps down to river level at the convention center. From there you'll be at the river's edge, passing under the 9th, 7th, and 6th street bridges. After the bridges the trail passes under the fort duquesne bridge and enter point state park.
One you enter the park you can take an asphalt ramp that meanders up to the portal bridge and museum or simply stay straight to arrive at the fountain.