Aurora is a trickier question than most places in CO. The problem arrises from the city straddling the Denver county line; Aurora itself is entirely within Adams, Arapahoe, and Douglas counties, but it's pretty tricky to tell where one county ends and another begins with the continuum of development. Since Denver has a special ability to regulate open carry, you've got to be careful that you don't cross over. Inside Aurora proper, since it's not in Denver, OC is legal everywhere that it's not specifically posted to be disallowed. Aurora actually bothered to ammend its municipal code after preemption was passed to reflect this, and I'll paste it below in case you want to print it out and carry it with you.
All that having been said, I have myself OC'ed in Aurora a few times and not had a problem. People may be more jittery about it so close to Denver than in other areas of the state, but I doubt you'd have any problem if you don't look like you're trying to cause any trouble.
Sec. 94-144. Unlawful concealment and display. (a)Concealment. It shall be unlawful for any person to wear under his or her clothes or carry concealed on or about his or her person any illegal or dangerous weapon, including but not by way of limitation any firearm, slingshot, razor, dirk, dagger, or any knife, nunchaku, throwing stars, or any illegal or dangerous weapon.
(b)Defenses.[/i] It shall not be an offense of subsection (a) of this section if the weapon involved was a knife or firearm, which was not an illegal weapon, and if the defendant was:
(1)In a private automobile or other private means of conveyance carrying the weapon for lawful protection of such person's or another's person or property while traveling; or
(2)In his or her own dwelling or place of business or on property owned or under his or her control at the time of the alleged violation; or
(3)A person who, at the time of carrying the concealed weapon held a valid permit to carry such concealed weapon issued pursuant to C.R.S. 18-12-105.1 as it existed prior to its repeal, or, if the weapon involved was a handgun, held a valid permit to carry a concealed handgun or a temporary emergency permit issued pursuant to pt. 2 of art. 12 of tit. 18 of the Colorado Revised Statutes; except that it shall be an offense under this section if the person was carrying a concealed handgun in violation of the carrying restrictions contained in C.R.S. 18-12-214; or
(4)A peace officer, level I or level IA, as defined in C.R.S. 18-1-901(3)(1)(I) or (3)(C)(II)1; or
(5)A peace officer, level II, as defined in C.R.S. 18-1-901(3)(1)(III), while on duty; or
(6)A United States Probation Officer or a United States Pretrial Services Officer while on duty and serving in the State of Colorado under the authority of rules and regulations promulgated by the Judicial Conference of the United States.
(c)Display. It shall be unlawful for any person to knowingly, recklessly, or negligently display, flourish, or brandish any illegal or dangerous weapon, including but not limited to those enunciated in subsection (a) of this section, in such manner as to reasonably cause fear of bodily injury to another person.
Sec. 94-154. Firearms prohibited in or upon public facilities.
(a)The carrying of firearms in or upon public facilities is unlawful when said facilities are posted with notification that the carrying of firearms is prohibited.
(b)Nothing in this section shall be construed to forbid any law enforcement officer from carrying or wearing such weapons and firearms as shall be necessary in the proper discharge of his or her duties.