I get the Muriatic acid from a local hardware store (True Value) and you can get the Super Clean from Wal-Mart.
I know folks seem to like other cleaners, but the Super Clean is by far the best for de-greasing - I had tried them all when I was into cars. The bad thing with Super Clean is that is it so aggressive - a lot of hobbiests use it to remove paint from detailed items. It tarnishes aluminum, too so be careful with it. I use it through a pressure washer to wash my MX bikes (lots of aluminum) so I can say that diluted it is fine on AL. Just be careful using it - at full strength it will chemically burn your skin (so will the acid).
Scott