The Lloyd Center lots are empty in the evenings. Security does chain off the driveways but it's an hour or so after the stores close which is 6 on Sunday's I think.
Same should go for the Jantzen Beach parking lots. I've been there in the evening when whole sections of the lots were empty even tho the stores were still open.
The lot behind the Point West Credit Union is pretty much empty after the offices closed. This includes both Saturday and Sunday. It's a large lot because it's shared with an office building next door. The Credit Union's address is 718 NE 12th Ave. It's located between Benson High School and I 84. The streets south of this lot are quiet also.
A short way out of the city are the Tannasbourne Mall to the west and the Outlet Mall to the east. Both are next to freeways. Travel time is short.
Kaiser Permanente offices are closed on Sunday. Their lots would be empty.