You might check out the course for the annual Wharf-to-Wharf race. http://www.wharftowharf.com/[/URL" target="_blank">

It's only 6 miles, but you could easily extend it if you run it backwards...start in Capitola, run to the boardwalk/wharf area and then continue on West Cliff Drive (nice flat running on a cliff overlooking the ocean). Or I guess you could start from Natural Bridges state park (at the North end of W. Cliff Drive) and run to Capitola and back.

Another option would be to drive up to Henry Cowell State Park in Felton (about 15 minutes from Santa Cruz). I'm not totally familar with the trails up there, but there might be a longer one that will suit your needs if you prefer to go off-road. http://www.parks.ca.gov/?page_id=546[/URL" target="_blank">

I lived in Santa Cruz for 5 years but I've been gone for 7 years now, so my memories are growing fuzzy. Capitola is not all that far from Aptos, so it might not be unreasonable to start a run there. I just think if you run in Santa Cruz and you miss out on West Cliff Drive, it is a crime!! I did a little hiking in Nicene Marks but didn't go too far in, so I'm not sure about the hills. San Andreas Rd. might work...It's been a long time since I drove that area but I don't recall it being too heavy with traffic. Good luck!