OK. So what if I take the job now, move to Mexico next month, and don't apply for my wifes citizenship until we get back in, say 2011. Does anyone know what kind of permissions she would need to leave for an extended period like that?
So it seems I'm coming to the party a bit late
I have several thoughts:-
i. If you leave now, and attempt to apply while living abroad, there is a high probability that your wife will be considered to have broken continuous residence (as others have already stated).
ii. If you leave now and plan to apply after you both return, your wife will need to wait 2yrs+1day from the date she returns before she becomes eligible once again.
iii. Assuming you are a USC, work for a US corporation, are being posted overseas on an assignment (by that corporation), and can prove it will last longer than 1 yr, your wife may be eligible to apply for expedited citizenship under 8.CFR.319.2
Personally I recommend you either get her citizenship sorted out now through the conventional route, or investigate option iii.