Soap and water with a low pressure rinse should do nicely, followed by a little auto wax, if you're so inclined.  Aluminum has fatigue problems, but usually only after high mileage.  If you clean the frame thoroughly, look for cracks in the paint or clear finish near welds and stress points.  If you sit on it and bounce a little bit, it shouldn't make creaking or pinging noises.  BTW, any used wheels with a few thousand miles on them should be inspected for cracks, too.