Solvang was last weekend, so too late for that one, but keep it in mind for next year. I have done the century twice, which has a good amount of climbing, but did the half century this time and loved the relatively low amount of climbing. The same or less than Palm Springs (which I have also done a few times including this year).
Just so you know, the amount of people at Palm Springs this year was CRAZY! I've never seen that huge of a crowd, which was frustrating not only at the SAGs, but for people trying to go faster than the majority. Could hardly get around anyone during some parts of that ride. But over all a great route. Glad you enjoyed it.
As for other rides, Cool Breeze is in August. They have a metric century, 60-ish miles with about 1500 feet of climbing (similar to Palm Springs and Solvang).
If and when you are ready to try a century, Amtrak is a good first one. It's two or three weeks after Cool Breeze, (beginning of September) so the Cool Breeze Metric would be a good training ride to build up your miles for Amtrak. Amtrak goes from Irvine to San Diego and you take a train back to Irvine. They bring your bike back for you in a truck after covering it in a blanket. Amtrak is probably the lowest elevation gain century around here. Might be comparable to Palm Springs Century, but I think it might actually be less climbing. I'd have to check. You have to register for Amtrak on a specific date in June. Check their website for the date. It sells out within a couple of hours, if even that, so you have to be at your computer at like 7:00 a.m. registering to get your spot.
I am aware of a lot of other "fun rides", but off the top of my head, these have the lowest elevation gain. You can look for events on active.com as well.