For a few more miles you can stay on Summit and go down Old San Jose Rd then ride along the beach back into Santa Cruz (clockwise), which I personally prefer. Also a lot of Hwy 9 has no shoulder. Graham Hill, Glen Canyon, or Granite Creek are all good alternates. I really like Glen Canyon because it's relatively short and very low traffic. This is my personal prefered routing:
http://www.bikely.com/maps/bike-path/example-2