When are you going?
I have never fished the Nehalem river itself, only the north fork, not sure but there's probably some fish in there right now, plenty in the bay that's for sure, the rain today might have pushed a few upriver. I would try that road, looks like it would have decent access.
That being said, from what I have seen there is not a hatchery on the Nehalem river. (correct me if I'm wrong), but I think the only hatchery in the Nehalem rivers is the one on the NF Nehalem (North Nehalem Hatchery). I know that NF Nehalem gets most of the coho also. Typically it's a zoo at the hatchery there but this year I haven't seen a single person. Maybe it has something to do with the fact that NF Nehalem is so low I don't think a tadpole could go up it.
Typically NF Nehalem is the more productive of the two, but right now it's really low, and although there are probably some fish in there, I don't think it's a great option. Even the mainstem Nehalem is really low...