The best way to grab this cache is to take one of the many busses that run along the SODO Busway (aka 5th Ave). The busway exists for about 1.5 miles and is lined with great murals.
5th Ave is bus-only, so I've indicated what I think is the closest legal parking. You can also consider walking over from the light rail, biking the SODO trail (it runs most of the same distance), or other non-car transit.
People often loiter on the east side of the street, so be aware of muggles. It also can feel sort of meh at night around here, but it shouldn't actually be unsafe.
Congrats to Laurie253 on the FTF!