I did it in 2013 - wanted PPL with Instrument Rating privileges, but found it easier to do full ATPL conversion (from AUS ATPL) to get IR privileges. The PPL conversion won't transfer across an Instrument Rating - to do that you need to do the IR written and then take the flight test.
In the end I was doing a type rating in the US in a sim anyway so did the written ATPL (not easy!!) and then did the ATP check ride in the sim.
PPL easy to get from an AUS licence with VFR privileges based on conversion across; CPL/ATPL or anything including an IR - much harder. Yes, you need to visit the FSDO in person (plenty in California or Hawaii) and it takes a little bit to set it up and organise an appointment and get them the paperwork.
The other problem was the lead times involved - CASA took forever to issue my licence copy to the FAA (you can't hurry this bit up) and then the FAA took even longer to issue my paperwork. So give it a lot of lead time if you have a set date that you need to use the FAA PPL.
The other complicating factor now is the security check required (since 9/11) for sitting a flight test (CPL/ATP or IR). It is completely over the top and made more confusing by being a foreigner - even people in the same government office in the USA could not agree on whether I needed to do it or not! In the end, the flight school you want to do the test with will need to advise you. Once again, this can be a very long and drawn out process (e.g. need fingerprints, but only two people in AUS do them for the FAA etc etc etc).
Good luck!