Paul from Quincy, IL on 10/13/2015 7:17:10 AM:
"It's a creepy station. Small and dingy."
It's true California stations are a lot nicer, but to call PGH creepy or dingy suggests the poster doesn't get out much. Yes is is small, but then it only servers 2 trains each way per day and is perfectly adequate.
To answer the original question, check the station page at amtrak.com for its hours. If it is open when you want to be there, then yes, do it. Your ticket entitles you to be be there, and besides it's not the kind of place where officious, paranoid security would hassle you.
We've arrived there from the west 4 times, and against all odds, the train was on time at 5:03AM and had to wait around almost two hours until dawn to head for the trail.