I wash my bike as soon as I get home from a ride on the beach road, every time. Our preferred ride is a little farther inland, for several reasons (less traffic, less wind, you can go in a loop rather than out-and-back; but also the salt). I had salt air corrode a brand new pair of polished aluminum hubs once, during a 60-mile ride, before I could get back and wash it.

My motorcycle chain and brake disks (which I'm not as diligent about washing as I am the velo ) rust very quickly in a coastal environment.