You can try it, but I think at 500mA it may not be as bright as you might suspect. I believe as a general rule if it says 500mA, you may consider that a max that will more than likely never occur.....can't tell you how much you can realistically expect, but others have said that rarely do wall worts ever produce thier rated (think displayed) current.
If you are just trying something, then fine, try it, if you want this for a real project, then spend the money on a quality 120VAC transformer.....like the MicroDrive series. Used them, nice, quality made product that is well made and EASY to use, install, and setup.
Bob E.