California is great, I loved my all too brief stay there a couple of years back when my wife and I stayed in Santa Monica on the way to Hawai'i. Its certainly a very lively place around Santa Monica Pier, lots of places to eat & drink (there's even a pub at end of Santa Monica Blvd!). Further afield there's so much to see, although the traffic can be hellish especially at peak times so I'd recommend if heading say Downtown using the recently extended Metro which will take some strain off travelling around. And of course there's Beverley Hills & Hollywood if a bit of celebrity spotting is the thing! Admittedly I prefer heading to Sunset Blvd to visit the famous Rainbow Bar n Grill, but that's because I'm into the rock scene and that is basically a rock fan's pilgrimage! Just be warned though, it will likely be very, very hot when you go so always keep the factor 50 & bottled water at hand, being such a densely populated place it seems to suck in the heat!
I've also been to Jersey (River Edge to be exact) which is a lovely state, think 'Home Alone' and you can imagine what the suburbs are like. And of course I've been to New York which is, well New York. You either hate it or love it, and despite it's vast size (especially when seen from a tour bus heading down Broadway!) I loved it.
But my favourite state? It has to be Hawai'i by a country mile. Its America, but slowed down even more so than California. Of course its a long way even from LA (a six hour flight from LAX), and has the slightly odd quirk of being far more popular with Japanese tourists than those from Europe, but the people are wonderful, friendly and relaxed.
So you'll have a great time out there without doubt, and although the flight is long, probably around 10.5 - 11 hours so long as either the plane has in-flight entertainment, or you take your own it can, well fly by!!