I didnt use the Darwin fish because it could raise anger of chirstians towards your company, since it is a symbol often used by evolutionists/atheists to criticize creationists.
Being a Publicity Agency, at least here in Brazil, logos should be a little abstract and colorful. It doesnt need to be understood at the first glance, because like that, people will say "ooohh, that what it means". The symbol should show creativity, be used without the words, and even like this, people will remember you.