Catalina Island is a short ferry ride from several points in the Orange County and LA County area, and it perfect for a weekend! The main town is Avalon, while most of the rest of the island is undeveloped. You can rent a golf cart and explore the streets of this island to get a real taste for how the residents live! Once you leave the main strip, you find loads of nature and (if you go a little more inland) some buffalo!
I highly recommend staying at the Hermosa Hotel, a couple of doors down from the Vons supermarket. They have small cottages that are very private and affordable. The location is super convenient too! (link is below)