Santa Cruz is one of the few places in the vicinity of San Francisco that seems to have a distinct flavour of its own. Surfing is clearly the primary passion in Santa Cruz.
Here is one way of doing a tour of Santa Cruz. First drive to Natural Bridges State Beach and park your car there. Not a hundred yards out into the ocean is the last remaining 'bridge'. The visitor center there has pictures of the bridge structures from 1900 through to this day and the wear and tear of nature is clear. The last remaining bridge still has a long way to go and is the perch for dozens of gulls, pelicans and cormorants. Another thing to look out for are Monarch Butterflies. Tens of thousands of them. The Monarch Butterfly Sanctuary is the destination for butterflies that have flown 2500 miles (that wasn't a typo. 2500 miles) from Canada to escape the winter. The best time to see these butterflies is in the winter months - Nov/Dec/Jan. Go there. You are guaranteed to be amazed when you see just how many of them are on the same tree branch.
From this point, the Santa Cruz Beach Boardwalk is about 2 or 3 miles along the shore. You can either walk or bike this. Along the way you will see richie-rich houses, bikers, runners and dogs. If you are going to walk your dog, then a roll of tissue paper is highly recommended! The road itself is called Cliff Drive and the cliff falls away about 30 to 40 feet to the ocean. I once even saw nude sunbathing there which I am faily sure is illegal. Summers can get very hot so you want to be careful about leaving stuff in the rear window of your car.
The winding road and the seaside sights themselves are pleasant enough. Then there is Lighthouse State Beach Santa Cruz has elevated surfing to some kind of a national service and right inside the lighthouse itself is a surfing museum. Along the way is a very nice statue of a surfer. Further down, the DMV has its own set of rules. By now the people around are not walking dogs as much as putting on/taking off their wet suits.
Another 10 minutes and you are at Santa Cruz Beach Boardwalk. Parking here is very unpleasant and after many visits I have learnt that it is best to park along the ocean and walk it to the Boardwalk. The Boardwalk is also a good fun place with all the usual attractions - video games, roller coasters, giant (ferris) wheels, assorted rides, bump cars, target practice - the whole works. The beach itself is very dirty though. If you are going there with your wife/girlfriend it is a good place to win a few soft toys without being very talented.
If you've gone all the way to Santa Cruz, it's not a bad idea to drive further south to Pigeon Point Lighthouse near Pescadero. Further down south is beautiful Big Sur.