Carroll Beek is located a half a block from the ferry on Balboa Island.
From PCH take Jamboree down the hill towards the ocean and across the bridge onto the island.
Go to the second stop sign and turn right on Park Avenue.
Follow Park Avenue all the way down the island to Agate. (There is a little restaurant on the corner on your left.)
It can be a good idea to go past Agate to the next street over and park there and stroll over to the Carroll Beek Center.
That way you avoid the ferry traffic.