Just to affirm and underscore the above: Open a Charles Schwab checking account (which will offer you all of their investment opportunities also, of which you need avail yourself of none). Schwab will issue you a credit card which will allow you to withdraw funds (local pesos...about 1,000 pesos a day limit here = $250 US), refunding your account at the end of each month the banking fees which you would usually incur ($16.50 pesos per $1,000 pesos withdrawn at going rates). Hence, you can get your cash without paying an exhorbitant extortion, which isn't the case if you use a standard credit card.
I'm only here four months at a pop, but find US cash in hand and a Charles Schwab checking account (to which I can electronically direct funds from my general checking account) the best and most conservative, trustworthy way to proceed.
If you are moving here permanently, you might look to Uruguay for a bank account.
GFW