The problem with Santa Cruz area is that they don't have life guards at all the beaches all the time. With the economy the beaches cannot have lifeguards at all the beaches so, they rotate around. The reason I know is that I recently took a bunch of girls scouts to the beach and one of the requirements was that the beach have a lifeguard if the girls wanted to enter the water. The original beach we picked did not have a lifeguard there that week. We ended up at Rio Del Mar beach. The waves were really big here and lots of surfers so, I imagine it would be great for boggie boarding...
You could always ask a lifeguard on the board walk and I'm sure they will let you know the best beach to go to.