There are races like Mt. Sac and Occidental that have entry standards (and some listed on Direct Athletics will require you to get permission to enter) but most do not have standards. You can go to the indoor meets at Northern Arizona or Air Force, outdoors at Ben Brown, two meets that Long Beach will hold at Cerritos, Steve Scott Invitational at UCI, Triton Invit at UCSD, meets at APU, all as a master without entry standards (none of these are masters meets).
Right now I'm getting ready to race at the Armory next month on an open weekend from my team's schedule.
The SoCal meets that you CANNOT race in as a master are the exception. Mostly these are college scored meets.