I spent Saturday riding a rented bike around Santa Cruz, CA. I rode all around Santa Cruz and along the coast to Natural Bridges State Park. With all of the traffic and one-way streets, a bike is an excellent way to get around.
If you get to Santa Cruz without a bike, there are a few places that rent them. Electric Bike Rentals is located where 3rd Street curves into Front Street. I rented a hardtail KHS mountain bike for $35 for an entire day and I got to keep it overnight. They also have electric bikes, which I saw plenty of zipping around town.
There's another place right on Beach Street at the eastern end of the Boardwalk. I don't recall the name of the store, but they rent heavy, singlespeed beach cruisers for $6/hour or $28/day. Just look for the sign that says "BIKE RENTAL."
You can also rent demos of high-end full suspension mountain bikes from the Local Bike Shops in Santa Cruz for about $50. FS for city riding is a bit overkill IMO, but there are plenty of trails nearby to check out.
Speaking of electric bikes in Santa Cruz, check out this program: Santa Cruz County gives county residents a $375 instant rebate on a new electric bike. Wow! Given that eBikes start at about $800, this is some kind of deal.