Hey Brenno,
What I can tell you from personal experience is this.
I'm pretty much doing your option 2.. I have a CASA PPL. Am currently over in California doing my IR. I was able to get an FAA PPL which is valid when I carry my CASA PPL, so that was easy (just some paperwork)..
Like your mate said, the flying is great in CA. I'm in San Diego - the school is excellent, instructor brilliant and in terms of professionalism, it really does beat anything I've experienced in Aus.. (sorry if you're reading this and are involved with an Aust flying school, but I'm just being honest..) Instrument flying is great here as you have so many options of airports nearby with all types of approaches - even ILS's - also, great experience with high traffic areas..and generally speaking, the planes are newer than many I've flown back home..
BUT... make sure you do ALL your sums.. by the time you add accomodation, car (?)/transport, airfare to get here, comms cost (phone), keeping in touch with back home, exchange rate.... it does start to get closer to what you're paying in oz...
I love flying here as I find I can dedicate myself to the task at hand, without all of lifes other distractions (friend, family etc).. I've been flying twice a day and study every night.. just helps you get things done quicker ... time is money!
I guess in short.. don't think you'll save a heap of money coming to the US .. if you are happy with your school, instructor & training, probably best to stay in OZ.. If it's for other reasons, I can highly recommend San Diego.. great town, excellent flying weather and awesome experiences.
Hope this helps a little