The answer is no, it is not even close to something we should be worried about.

Is that because it's going to be diluted to unnoticeable levels even near the origin?

Yes

Unless, of course, you're a homeopath. On a slightly more serious note, I would expect to see a variety of illnesses occurring at a statistically ordinary rate around the variously-projected times of arrival to be blamed on radioactive seawater regardless of the actual concentrations (which will probably be in the high-C, or incredibly powerful because it's incredibly weak, homeopathic dilution range).

>Is the US West Coast at danger of increased incidence rates of radiation related illness?

No.

Remember the US used to do multiple nuclear detonation tests off Pacific islands after WWII. The Pacific Ocean has a lot of water to dilute the effects.

We've been dumping far worse radioactive waste in the Pacific for years.