It's a better idea to enjoy it in the daytime with the kids. Downtown Portland is a different place at night.
There are homeless people in the park day and night. Also in doorways in buildings near the park. But I feel the park is safe and it is very beautiful at night with the city lights all around.
I've never had a problem there, but I guess they do happen now and then. As others have said, it's probably best to bring kids during the day and be part of a group, if at night. But I don't think I have ever been through at night other than alone, and have never had a hint of a problem.
I wouldn't recommend going at night esp. with kids. Best to stay in a group IF you want to be downtown at night.
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