One product I've used for years is "Pedro's" Biodegradable De-Greaser. It's a pump-spray bottle, works pretty good and I haven't noticed any problems on my paint or aluminum finishes. (Note: This is a spray on-hose off sort of cleaner, but I use a soft cloth afterwards to prevent splotches and haze)

Just a suggestion.

-3Bikes

P.S. Don't forget to use chain lubricant and rust protecter on brake calipers, axles, gears..... that sort of thing.