Assuming you will not be receiving any type of foreign earned income during your travels, you file your tax returns as you normally would. For your mailing address use an address where the IRS can contact you if ever required.
Note that any tax refund can only be direct deposited into a US bank located in the US.
If you are going to use TurboTax any online account fees can only be paid with a US credit/debit card with a US billing address.
You can e-file a tax return using the TurboTax online editions from anywhere in the world with an internet connection.
