This is definitely something to do on a weekday. We recently visited Pittsburgh, and on the weekdays, we were pretty much the only people riding on it. Once Saturday hit, there were lines out the door for it!
Also, on Friday night we were trying to get back down and it broke/malfunctioned. We waited a while to see if it could be fixed (since we had already bought a round trip ticket), and then just ended up taking an uber back to our hotel.
Exact change is needed (you pay at the top) or you can use a credit card at the bottom.
Also, sit in the bottom car if you can! Best view!