There are some great routes in the Santa Cruz area, but some require some climbing. One of my favorites is to go North on Hwy 1, do the Swanton Road Loop, continue north and take Gazos Creek into Pescadero for lunch. Then you can come back Hwy 1 past the Pidgeon Pt. light house and Ano Nuevo. That's a good 60 miles or so. If you want a longer route, you can go from Pescadero up Stagecoach to San Gregario and come back Hyw 1. That'll put you at about 80 miles.
There's also routes through the Santa Cruz Mountains along Skyline and the Summit. Eureka Canyon is always a nice ride, but you have to climb a bit.
As far as south -- I tend to avoid going through the Watsonville area. There's little to no shoulders on the roads for some stretches and the cars and farming equipment come a little too close for my tastes.
PM me and I'll try to help you pick a good route.
Susie
"It never gets easier, you just go faster." -- Greg LeMond