Don't know too much about putting leagues in SoCal. But if you want tournament action check these out:
West Coast Disc Golf's FB page for info on weeklies & monthlies at La Mirada & Huntington Beach. LaMi's not too far from Costa Mesa. Huntington Beach is even closer.
Lake Forest Disc Golf's FB page for info on a new disc golf course on a ball golf course. I haven't played there yet but I know they run weeklies and monthlies there. Lake Forest is close to Costa Mesa too.
Lots of weeklies & monthlies closer to LA too @ Oak Grove, Verdugo Hills, Sylmar, etc. Oak Grove DGC's FB page has a lot of info for all that.
If you're interested in PDGA events, check out SoCal Disc Golf Association (they have a Wordpress site and a FB page) which runs a year long points series of PDGA B-tiers & C-tiers from as far south as San Diego up to Bakersfield. The SoCal series usually runs from December with the XMas Open at Sylmar in the San Fernando Valley to the following Novemeber with the SoCal Championship which has recently rotated between locations year to year. Depending on the year and on the will of individual TD's & clubs, there are around 20-25 PDGA SoCal events between San Diego, Orange, LA, San Bernardino, Riverside, Ventura & Kern counties.
No shortage of tournament action, to be sure. 12 months a year in SoCal.