Depends on what sort of hole you need- how precisely cylindrical,
perpendicular and located. (Which you don't specify.)
Hole--saw will hack a hole, with pretty rough sides. Use water-soluble
oil to cool both the material and the cutter. Aluminum melts readily,
and will clog the cutters. WD-40, being mainly kerosene, is probably
not what you want to use for coolant. Keep tool-speed down.