Yes, that was my first thought as well. You can join a dive tour at Catalina Divers' Supply, they are used to people coming from all over, without cold water experience. But that's a long day, even from Ventura. I looked around briefly and it seems like there is not a lot of shore diving in the area, due to the cliffs. So a drive down to Laguna Beach or up to Monterey is not that convenient.
Near Ventura, Deer Creek was the most convenient dive spot for a shore dive, but with the big surf a couple of months ago the stairs collapsed and no longer reach PCH. County Line beach is next closest to the south, but you'd have to find a calmer day there. In Malibu a few minutes down PCH there are lots of spots for an easy beach dive where you can get your weight dialed in, as well as experience diving in a thicker wetsuit than needed for FL waters.
I usually take beach dive virgins to either Escondido Beach or Malibu Rd in Malibu, as both are easy shore entries with convenient free parking. And are good for local checkout dives. Or Leo Carrillo north parking lot once it reopens after the flooding a couple of months ago. There are other spots as well if all you want to do is get in the water, do weight checks and blow some bubbles under water
You should definitely get your wetsuit, gear and weighting sorted out before spending $$ and a day on a boat trip. This past weekend, shore diving was really good