California is a huge state, avoid southern california its over crowded and the traffic is horrible. Unless your planning to go to Anaheim to see Disneyland, or Sea World or the Zoo in San Diego its not worth hanging out there.
I lived in both southern and northern California and there is no comparison. If you go north avoid San Francisco the bridge looks the same in postcards. Sacramento is nice they have water, bridges and museums. If you never seen the Pacific Ocean head to Bodega Bay north of San Francisco its a pretty spot and quieter than most California beaches. The redwoods are nice too continue north, you can’t miss them 🙂

orange county (good beaches) can be chilly at night though, so im not sure…

It depends on what you’re looking for. If you want the night life, restaurants and clubs, San Francisco and LA (check out Huntington beach!) are where you want to be. If you want something quieter, I’d recommend the north coast of California. There are some beautiful towns up north like Bodega Bay and Jenner where you can just take in the sea air and be alone with nature and your thoughts and stay at a Bed and Breakfast. You can also pass through the Napa Valley Vineyards to get there. Carmel and Monterrey are also beautiful towns with beautiful beaches but they’re a little more touristy and expensive.

Orange County– hungtinton beach is really nice (and all the beaches that are around that area). It’s also near L.A. and San Diego, so you could visit them too. =)

San Francisco is also a really nice city. The only thing about S.F. is that the weather isn’t all that great during April. It can get chilly, but there is a good chance it will be sunny! =)