Skip the overpriced and restrictive Golden Triangle for Pittsburgh bike rentals and visit these guys. Was just there this past weekend on the 4th of July to rent some bikes for a couple hours and ride around the city to enjoy the day. Amazing selection of everything from sport bikes to stylin' old vintage cruisers (which I went for!). VERY reasonable rental prices, and an amazing array of stuff to look at at the museum/shop. I'm an Americana freak and I was in, well, heaven. You could spend hours in there.
For renters, they're right along the riverside trail so you can bike just a couple clearly labeled blocks and be right on your way with access to all the trails in the city area. The guys were friendly and knowledgeable. I wish I still lived in the area - I'd be here all the time and I'd definitely buy a bike from them (I fell in love with a vintage Schwinn I might go back and buy anyway, honestly). Hidden gem of Pittsburgh - if you stop by just be sure to drop them a cash donation - well worth it and well-deserved!