Hello "New Gun Owner", you can carry a loaded handgun in public at the age of 18 as long as you do not live in a city or county that has a banned against loaded carry to Non-CHL holders, this is under ORS 166.173
166.173 Authority of city or county to regulate possession of loaded firearms in public places. (1) A city or county may adopt ordinances to regulate, restrict or prohibit the possession of loaded firearms in public places as defined in ORS 161.015.
(2) Ordinances adopted under subsection (1) of this section do not apply to or affect:
(a) A law enforcement officer in the performance of official duty.
(b) A member of the military in the performance of official duty.
(c) A person licensed to carry a concealed handgun.
(d) A person authorized to possess a loaded firearm while in or on a public building or court facility under ORS 166.370.
(e) An employee of the United States Department of Agriculture, acting within the scope of employment, who possesses a loaded firearm in the course of the lawful taking of wildlife. [1995 s.s. c.1 §4; 1999 c.782 §8; 2009 c.556 §3]
You are correct, since you do not have a CHL, you can not go into public buidings and capitol building with any firearm. Don't forget, even though you do get a CHL, you still can not go into court buildings and Federal Buildings.
166.370 Possession of firearm or dangerous weapon in public building or court facility; exceptions; discharging firearm at school. (1) Any person who intentionally possesses a loaded or unloaded firearm or any other instrument used as a dangerous weapon, while in or on a public building, shall upon conviction be guilty of a Class C felony.
(2)(a) Except as otherwise provided in paragraph (b) of this subsection, a person who intentionally possesses:
(A) A firearm in a court facility is guilty, upon conviction, of a Class C felony. A person who intentionally possesses a firearm in a court facility shall surrender the firearm to a law enforcement officer.
(B) A weapon, other than a firearm, in a court facility may be required to surrender the weapon to a law enforcement officer or to immediately remove it from the court facility. A person who fails to comply with this subparagraph is guilty, upon conviction, of a Class C felony.
(b) The presiding judge of a judicial district may enter an order permitting the possession of specified weapons in a court facility.
(3) Subsection (1) of this section does not apply to:
(a) A sheriff, police officer, other duly appointed peace officers or a corrections officer while acting within the scope of employment.
(b) A person summoned by a peace officer to assist in making an arrest or preserving the peace, while the summoned person is engaged in assisting the officer.
(c) An active or reserve member of the military forces of this state or the United States, when engaged in the performance of duty.
(d) A person who is licensed under ORS 166.291 and 166.292 to carry a concealed handgun.
(e) A person who is authorized by the officer or agency that controls the public building to possess a firearm or dangerous weapon in that public building.
(f) An employee of the United States Department of Agriculture, acting within the scope of employment, who possesses a firearm in the course of the lawful taking of wildlife.
(g) Possession of a firearm on school property if the firearm:
(A) Is possessed by a person who is not otherwise prohibited from possessing the firearm; and
(B) Is unloaded and locked in a motor vehicle.
(4) The exceptions listed in subsection (3)(b) to (g) of this section constitute affirmative defenses to a charge of violating subsection (1) of this section.
(5)(a) Any person who knowingly, or with reckless disregard for the safety of another, discharges or attempts to discharge a firearm at a place that the person knows is a school shall upon conviction be guilty of a Class C felony.
(b) Paragraph (a) of this subsection does not apply to the discharge of a firearm:
(A) As part of a program approved by a school in the school by an individual who is participating in the program;
(B) By a law enforcement officer acting in the officer’s official capacity; or
(C) By an employee of the United States Department of Agriculture, acting within the scope of employment, in the course of the lawful taking of wildlife.
(6) Any weapon carried in violation of this section is subject to the forfeiture provisions of ORS 166.279.
(7) Notwithstanding the fact that a person’s conduct in a single criminal episode constitutes a violation of both subsections (1) and (5) of this section, the district attorney may charge the person with only one of the offenses.
(8) As used in this section, “dangerous weapon” means a dangerous weapon as that term is defined in ORS 161.015. [1969 c.705 §§2,4; 1977 c.207 §2; 1979 c.398 §2; 1989 c.839 §22; 1989 c.982 §5; 1991 c.67 §39; 1993 c.625 §1; 1999 c.782 §7; 1999 c.1040 §4; 2001 c.666 §§24,36; 2003 c.614 §6; 2009 c.556 §6]
166.372 [1993 c.625 §3; repealed by 1996 c.16 §5]
Also, do not forget about the Federal law on the Gun Free School Zone Act. That means if you do not have a state license of carry a firearm, then you can not be in a 1000 feet radius of a K-12 school. Yet, I presumed this law can only be enforced by federal agents only.