Was there any organized worship of God before Mount Sinai?
No. From Genesis 1 until Exodus 20, there were no written do's and don'ts from God, and no single item of God-instituted worship. Sacrifices may have been brought, but no organized system of worship existed until Israel gathered at Mount Sinai.
Les explains that from Genesis 1 until Exodus 20, God had never given written do's and don'ts concerning what men could and could not do. He also states that there had not been one single item of God-instituted worship until the nation gathered around Mount Sinai. Les acknowledges that people probably brought sacrifices, but so far as having an organized system of worship, there had been none. At Sinai, after the 430 years were completed, God was getting ready to do something totally different than He had ever done before.