Stop worrying abou fire-roads. Don't pave trail along Highway 1 from Sanat Cruz. Give nature the respect you want to be given. I am a nurse. I am ususally a hiker.
Safety is allways a concern as well as maintainence of nature.
Due to potential dangers separate paths should be used for these two actviies respectively. Generally, most bikers OK, considerate. May be different if too crowded. Park authorities try. Pack your trash.