Be a kid.
Don't rule out a childhood-inspired romantic weekend. Stay at one of the Disney resort hotels in Anaheim and you can play all day in the park and then enjoy fine dining, concierge services and great views of the park back in your room (although the Disney's Grand Californian Hotel and Spa is probably the most "adult friendly"). Sea World in San Diego is another great destination if feeling like a kid is a must for your romantic weekend. Sea World has rides, animal shows and seasonal special events like music festivals and holiday celebrations with the animals.
Soak up the sun.
California is well known for its many wonderful beaches all along the coast. Whether you like to surf, swim or just bask in the sun, some of the most popular beach areas are Long Beach, Venice and Malibu. There are also many wonderful cove beaches created by the cliffs in areas like Santa Barbara, La Jolla, Jamala and San Clemente. Beaches like Venice and Malibu offer a trendier ocean town setting, while the cove beaches offer a bit more seclusion.
Live like a star.
Beverly Hills has many more zip codes than 90210. If you think glamour is romantic, then this is the place to be. Of course the weather's usually great and the shopping as famous as its inhabitants, but Beverly Hills also has great restaurants including Il Cielo which has been called the most romantic restaurant in Los Angeles. Finding a great area hotel isn't hard either and most offer amenities that are meant to pamper.
Heat things up in the desert.
Palm Springs, although famous for its golf courses, is also a great place for romance. If you're an outdoors couple Palm Springs offers bike riding, hiking or horseback riding. If you prefer to move a little less, there are hot air balloon rides overlooking the desert, casinos, shopping, theatrical and musical performances and museums. Palm Springs and the surrounding areas Palm Desert, Indian Wells and Desert Hot Springs also have day spas and spa resorts for a relaxing romantic weekend.