It'll take longer than 3 weeks in any event: it's about 7,000 sea miles. But there would have to be stops for
provisioning, refueling, so the mileage could grow. If you get seasick it would be more weeks of hell with the
medical possibility of death by dehydration.
If you are experienced sailors, it is the milk run. If you have friends who need crew maybe they'd take you. Some people take on crew who pay them for the experience, etc. There are options.
Please just remember, you're entering an unfamiliar
environment in which you must have life support systems to survive...I refer to the
boat, the ocean doesn't care at all if you live or die.
Crewing with strangers can be dangerous and
wind up not being fun; on the other hand, it could
work out okay. Think about how you'd select a
skipper.
Or maybe I misinterpreted your OP. CF is mostly folks with their own yachts and wannabes. Did you mean
cruise ship LA to SyD? or sailing yacht? One option you have is to fly LA to
Tahiti, spend some time there, and fly on to SYD. There are
charter yachts available at Raiatea, that people hire and sail to BoraBora and back. Island steamers within
French Polynesia. Depends a lot on how high on the hog you want to be.
Ann