You can also check under the cover to your fuse box or on the side of your glove box. When a car is shipped new to a dealer it comes with, among other things, a sticker that has the vehicle's radio code printed on it. When the Acura technician inspects the car before sale, sometimes they put the sticker in either of those two locations.
If you can't find it, there's a guy at Hondatech who can pull codes for pretty much any honda/acura, but you will need the
complete serial #
http://www.honda-tech.com/showthread.php?t=1726874
All else fails, head to the dealer. Just pull the radio yourself or they'll charge you like $100 for the service. Good luck.