Hi Lionel1946,
I also live in Southern California, in Ventura County. Before the pandemic, I would typically attend at least two train shows a year hosted by the "Great Train Show" organization. You can find their schedule on the trainshow.com website. According to the website, they won't be hosting any shows in So Cal this year. If you can hold out until the first quarter of 2023, they show three upcoming shows:
February 11-12 - Costa Mesa, CA
February 18-19 - Ventura, CA
March 18-19 - Victorville, CA
John