When I bought mine from WalyWorld, Mine was advertised as Aluminum. Others have stated that they have seen a steel version as well. In the last post of my PJ's failure, I put to rest that mine was aluminum.
I used a N45 disk magnet, VERY STRONG. The magnet did not stick to any portion of the frame. Just parts that were already know to be steel.
So since you might be in WallyWorld, take a look around for a product that has any form of magnet, (I am sure you can find something) take the magnet and touch it to several sections of the frame. If it attaches, it's steel. If you find a steel one,,,,,,I'd say get it!!! It did make a very nice build.
I feel ciertian, that if I had the steel version, my bike would still be out cruizing around.