I agree with you, Carrie ! The present perfect has to be translated by the French present simple. Carrie's translation is perfect, as far as time is concerned.
As for the translation of "sign", it depends on the context, I think...
Now that the grammar is sorted out, what kind of sign are you referring to? Depending on context sign can be:
une pancarte - smallish sign you make and post somewhere
une enseigne - long-term sign you put in front of a shop
une notice - an administrative sign notifying of something
un panneau - road sign or advertising