Conosca > Conozca

This is an advertisement I came across recently in the streets of Los Angeles which serves as an example of two things:
1) The prevalent use of the Spanish language in this city, in many settings acting as an unofficially official second language, as is the case throughout California, and other states in the Union.
2) A spelling problem that seseante communities are faced with, at times: writing <s> when the norm calls for <z> (or <c> before e and i). Here, we see conosca instead of the correct conozca.

The correct form should be conozca

As a side note, in other Romance languages, the same verb forms are indeed spelled with <s>: Italian conosca, Romanian cunoască vs. Spanish conozca. The change from s to z was a Spanish development, as can be seen from the original Latin form COGNOSCAT.