Where you look to find out is ORS 166, in particular ORS 166.170 and following. Carefully read all the regulations.. remember to note this concerns "concealed" weapons. look carefully at ORS 166.250(1)(c)(A), then read ORS 166.250(3) If it is in a holster on your hip, it is not to be considered "concealed" and many restrictions go away. Also pay attention to ORS 166.260.
If all else fails and you are still nervous, ask a lawyer or a judge. Oh yes, and be careful of ORS 166.360-380. If you will look at ORS 166.360ff you will see there laws concern "possession" not a "concealed" weapon. Where the law concerns "possession" it applies to any possession, not just concealed possession. Those you want to know very well as they will apply to your unlicensed OC too.
Be careful up around Portland. There are local government jurisdictions that have made use of ORS 166.173, and restrict LOADED unlicensed OC in their jurisdictions...OK? Read the law, study the law, know the law, and you will be able to abide the law.
It states: "is under the age of 18" And in ORS 166.250(3)