Santa Cruz beaches are not in the Golden Gate National Recreation area so they're wide open to metal detecting. If you go further North toward San Francisco you start getting into the National Park system where metal detecting is strictly verboten.
You don't need any permits to metal detect in the Santa Cruz area.
My father has done really well on gold rings at the main beach in SC starting from the South side of the pier and working down the beach in front of the big arcade/fun house where the rides are. I've only found silver there. There's a good parking lot on the North side of the pier with steps right down to the beach.
A short drive further South takes you to a big public beach at the South end of the Santa Cruz Harbor. We've done well on clads, and some silver jewelry there.
South from there is Capitola which can be either really good or a complete waste of time depending on conditions. We've found a decent number of gold and silver rings, tons of clads and a few silver coins. We've had heavy rain this season so the river there may have scoured out a lot of sand which could get you to the goodies. Capitola has more iron junk than I've seen at just about any other beach. Lot's of rusty nails and spikes. We use Excaliburs there so the iron isn't a problem for us. If you have hip waders you should bring them to hunt this beach so you can walk across the shallow area of the river. That way you can hunt both sides of it without having to make a big detour along the street. Be careful though because the water runs swift. The shallowest area is down by the ocean break. This time of year parking should be easy there but beware that the parking meter guy is really good. The second your meter expires he'll be there to write you a ticket. Bring a timer with you when you're on the beach.
Further South of there are more beaches like New Brighton State Beach. State parks don't care if you use a metal detector so you could check those out too if you have time. Pick up a tourist map and it will show where all the beaches are.
There are miles of beaches to hunt down there. Your best bet will either be the main beach with the arcade or Capitola.
So I put you some good spots....I figure....well (scratching my head) every fifth gold ring, every tenth silver ring and every tenth silver coin will suffice for my cut. Just PM me and I'll give you mailing directions so you can send me the loot. If you get into gold coins I figure we can split 50/50
Let me know how you did when you get back. We haven't worked Santa Cruz yet this season. Most of the local detector guys down there are really friendly so if you see some of them while you're there don't be afraid to say hi to them. If you have any more questions let me know.
Good luck!