Good afternoon Geoff:
Residency requirements will vary from state-to-state, but most plans require only that you have a permanent U.S. address and valid Tax I.D. in order to open an account in order to comply with Patriot Act requirements. I'd call the plan or plans you're interested in, tell them your situation, and see if they can accommodate you.
VP, Research & Development
This information does not constitute tax advice and is provided for informational purposes only. Please consult your tax advisor, financial advisor, local taxing authority, and/or plan provider or sponsor for more information.