Pacific Avenue is the main commercial street in downtown Santa Cruz. It's full of restaurants and various shops. The two streets parallel to Pacific also have some shops and eateries. There are drug stores, grocery stores, and most of life's basics in that neighborhood.
The Santa Cruz Beach Boardwalk is Santa Cruz's most popular tourist destination. It's a beach-front amusement park with carnival rides, a video arcade, games, and an old-school wooden roller coaster. Admission is free, and you can just pay for a few rides, or you can splurge on a day pass. It's very touristy, but still pretty fun to see.
The Beaches and ocean! There are lots of great beaches in Santa Cruz, though the very cold water might be a rude shock for some of you folks coming from Florida! Ocean kayaking is easy (most days) and superfun. You'll almost certainly see seals and otters and maybe more. You can rent kayaks at the Santa Cruz Yacht Harbor, or off the Capitola Wharf. Let us know if you want more details.