I converted my CASA CPL to FAA PPL a few months back, and even though it says the verification process takes 45-90 days, I got my fax back from Oklahoma City about a week after I sent it to them.
Once you send your form 452 to CASA to allow them to give the FAA details, they send it straight to the FAA, so as long as CASA are quick, then the feds are also really quick.
It also says it takes at least 2 weeks to make an appointment with an FSDO, which wasn't the case.. they aren't too busy these days, so depending on where you are going you should be able to make a booking straight away.