First, talk to an accountant that specializes in foreign earned income. I am not an accountant.
If you are a US citizen, you must still file US taxes. Be sure to fill out form 2555 which will allow you to claim an exemption of just under $90K USD for your foreign earned income. In other words, as long as you make less than this amount, you will not owe any US taxes. You must, however, still complete a US tax return even if you do not owe any tax. Tax returns are completed in USD, so you will just convert the Pesos back to dollars for the purposes of completing your return.
Check out the IRS website and do a search for form 2555. You will find lots of details. The key is to being eligible for this exemption is that you must live outside the US for 330 calendar days per year (physical presence test).
There is also the issue of income taxes in Argentina. Technically speaking, you would owe income tax in Argentina if you are present in this country more than 180 days per calendar year. Argentina does not have a tax treaty with the US.