There's a couple of Hotels that have some plastic boats for rent in Mission Bay. Someone here will have the details, but I don't think there's any place else. California is the land of litigation, lawyers and insurance companies, so it's pretty difficult to just rent small boats here. Most small boat rental places that I know of require some sort of certification, and usually from their courses. Insurance companies like boats with motors on/in them, so it's actually easier to rent powerboats or sailboats with engines. We used to rent cats off the beach here in Santa Cruz, but those days are long gone.
No cats though, unless things have changed(back):
http://www.catamaranresort.com/activities2.html?main=nav4&sub=sub2Hobie Getaways:
http://www.seaforthboatrental.com/sailboats/index.phpGood luck.
J
