Tillamook County public transportation district provides bus service centered around the community of Tillamook, but several of their services reach to surrounding areas. This includes a single bus route that connects Tillamook to Manzanita and Cannon Beach. It is considered a "Deviated Fixed Bus Route" as it has a regular route along highway 101, but riders may request that the bus be diverted from its route by up to ¾ of a mile to get to their destination. To be picked up at one of these deviated route locations, it is necessary to inform the transit agency beforehand when and where you would like to be picked up.
In keeping with this ¾ of a mile policy, it is possible to get reasonably close to Nehalem Bay State Park by public transit, but it isn't possible to get very far at all into the park.
The bus only goes through this area six times per day on weekdays and Saturdays, with no service on Sundays.
Connecting routes in Tillamook allow one to go all the way into downtown Portland if desired.
Fares depend on the distance traveled, with the cheapest fare $1 for the zone from Manzanita to Rockaway Beach.
Nehalem Bay State Park is the location of the Nehalem Bay landing strip / Manzanita airport. It is basically a paved air strip, with "primitive" (no services at all) camp sites near the runway for those that wish to arrive and camp by airplane.
I'm no pilot and have never flown into this place, but there are several hazards that seem fairly obvious to me:
1. There is a severe cross wind here. The air strip runs north-south, but the wind usually comes directly off the ocean, and is usually quite powerful.
2. There are deer and other reasonably sized wildlife in the area (elk, for example, have been seen). It would not be unexpected for them to graze along the landing strip.
3. There is no control tower or lighting here. Expect weather to cause problems from time to time.
If you can't land here, there is a reasonable airport (complete with an actual building) at Tillamook, which while fairly far south is at least a place to land that is somewhat more sheltered than the nearly beach-side landing strip here.