If you mean Los Angeles and not Louisiana, this is going to be harder. Many of the California Panhellenic Associations just aren't as active. I would certainly start by sending them an e-mail to see if they have any events (generally in the late spring or early summer) for prospective rushees. You wouldn't be attending their regular events, which are strictly for sorority alums.
A great source of information on every aspect of sorority recruitment is the website GreekChat.com. Look under the topic "sorority recruitment".
An important point is that sorority recruitment (and the sorority experience) varies widely depending on the college you are planning to attend. Do not get discouraged reading the stories of women rushing in Southern schools, which are unusually competive.
If you know the school you will be attending in the fall, look at the website for that school's panhellenic association (not for recs, only alums can write recs, but for information about the schedule and chapters). Then look at the individual chapter websites to get a sense of their activities, sports and social life.
Finally, I'm happy to answer whatever questions I can.