I live in the Seattle area, which is struggling with public drug use just like Portland. Like Portland, we've lived for decades with very progressive politicians who have lead successful decriminalization efforts and spent huge sums of public funds on treatment and harm reduction programs. After several decades and many, many millions of dollars spent, the problem is, by every measure, absolutely the worst it's ever…
I think other cities bussing and flying homeless people out west outweighs every possible policy change. We’ll never know if any of these policies stood a chance due to the USA viewing the west coast as a dumping ground for homeless people. Next time you’re passing by these people, ask them where they are from originally. Locals are like 20% of the problem.
Portland is better housing-wise, but not by much. Considering how most people who are both homeless and on drugs were homeless first, then turned to drugs, I think this is a strong confounding factor. It's hard to saw what effect decriminalization has had on drug use when it's adjacent to a housing crisis that is manufacturing more homelessness and drug use all on its own.