Hydrogen Peroxide and Hydrochloric Acid Etching
Your big problem is that the first step which occurs is not dissolving aluminum - it's dissolving aluminum oxide (alumina) which has formed on the surface of the metal. Your acetone cleaning got oils and such off the surface, but it didn't touch the oxide layer. Copper, for instance, doesn't oxidize quickly, so cleaning is important. With aluminum the situation is different. And the oxide layer is self-renewing, as PlasmaHH has noted. Bare aluminum will grab oxygen out of water, producing hydrogen gas, so dilute acids don't do well.

You may be better off using a hot, saturated sodium hydroxide solution, but there are two caveats. First, that stuff is really nasty if you get it on you, and eye protection is an absolute must. Second, I have no idea how well your resist will hold up.