It takes a few weeks to adjust to driving. We've been here in California for nearly three months now, and I think we've adjusted. I very occasionally have these minor moments of panic where I think "he's coming right at me - Aaaargh", but they're getting fewer and further between.
Something I do find is when I imagine myself driving at home (ie. in Northern Ireland), especially on rural roads, I can't remember which side of the road I used to drive on. I have to really think hard. ("Well, if the steering wheel was on that side, and we have the steering wheel closest to the middle of the road, that means we drive on this side. That means I .... hey! why is he driving on the wrong side of the road?! Aaaargh. *whimper*")
Something I do like about driving here is how relaxed it is. I think it's something to do with big wimpy engines, automatic gearboxes, soft suspension, wide roads and plenty of them. Folk mostly don't rush when driving. It's not as much like a race as it is at home (in NI).
And the thing I really like about driving here is turning right on red lights: if you come to a red light, and you're turning right (that's the "easy turn"), you can just treat it like a stop sign.
Oh, and parking here is dead easy. If you can parallel park, you'll probably never really be stuck for somewhere to park. Just don't park in front of a fire hydrant, or where the curb (sic) is painted red. Or yellow. Or blue. Or where the signs say you can't.