Dolphins don't have hands to write with. Nor did we invent a communication system by which dolphins and humans can communicate ideas.

Humans have had spoken-word history long before written. Native Americans for example. Dolphins may have something similar, perhaps a "show and tell" of sorts, who knows, but I admit it's obviously not as evolved if they can't avoid an annual slaughter.

Another extremely intelligent creature is the octopus, I wouldn't mind them having some protection as well. But they aren't as "sexy" as dolphins so I don't expect that to be forthcoming any century soon.

I'd guess communication methods available to dolphins aren't as good as those available to humans. I think all aural communication that is available to dolphins is available to humans, and yet we use mostly speech and gesticulation, both of which seem to be either unavailable or very limited for dolphins.

As for the octopus, by quickly browsing the usual suspects you can find that quite a lot of people find them much more sexy than dolphins, but let's not get to deep into that.

While dolphins lack the communication methods available to humans, I believe that they have the same methods available to them that whales possess. Whales have a pretty sophisticated "culture" that is encapsulated in the variying songs of different species and among the various geographic and tribal groupings within a particular species.

Yes, I know about that. I just doubt that it's as effective at expressing precise meanings as methods available for humans ("area within 100km radius from 33.593316 135.943022 is to be considered unsafe," and let's not get started on bordering the area with 3 meter high fences topped with barbed wire).