Peter's explanation is correct as is his conclusion that you do not need to block the nozzles. The cold start nozzle just gives an extra squirt of fuel to help start a very cold engine (under 14°). Even though the control rack is set to full enrichment when the engine is cold, the extra bit of fuel from these nozzles helps start a very cold engine. After you've started, the thermostat regulates the mixture up to about 113°. Since you live in Southern California I don't imagine these nozzles really ever come into play for you anyway!
Now if you remove them you might save ½ an ounce each. Think of the performance improvement.
