Is exchanging money at a cueva illegal?

Technically, it operates in a legal grey area, but it is the standard practice for almost every tourist and local in Argentina today.

Can I use my credit card?

Yes, foreign credit cards now receive a rate close to the MEP rate (similar to the blue dollar), but cash is still king for smaller shops and restaurants.

How do I spot a fake bill?

Only exchange at reputable cuevas recommended by locals. Count the money in front of the clerk before you leave the counter.

Getting the Best Exchange Rate in Argentina: The Blue Dollar

To get the 'blue dollar' rate, do not use your bank cards for cash withdrawals, as these default to the official rate. Instead, bring crisp, high-denomination USD bills and exchange them at authorized 'cuevas' or Western Union locations to nearly double your purchasing power.

Bring fresh USD. Only bring $100 bills. They must be brand new, crisp, and free of any marks, tears, or ink stains. Smaller bills (like $20s or $50s) get a significantly worse exchange rate.
Locate a 'Cueva'. A 'cueva' is an informal exchange house. In Buenos Aires, walk down Calle Florida; you will hear people shouting 'cambio'. If you are nervous, ask your Airbnb host or a local shopkeeper for a trusted contact. Avoid exchange booths at airports or banks, as they use the official rate.
Use Western Union for digital transfers. If you don't want to carry stacks of cash, use the Western Union app to send money to yourself. Pick it up at a local branch. They provide a rate very close to the blue dollar, and it is significantly safer than carrying thousands in cash.
Negotiate the rate. Check the daily rate on sites like 'dolarhoy.com' before you go. When at the cueva, show your bill, ask '¿Cuál es el tipo de cambio?', and verify the math before handing over your money.

Is exchanging money at a cueva illegal?: Technically, it operates in a legal grey area, but it is the standard practice for almost every tourist and local in Argentina today.
Can I use my credit card?: Yes, foreign credit cards now receive a rate close to the MEP rate (similar to the blue dollar), but cash is still king for smaller shops and restaurants.
How do I spot a fake bill?: Only exchange at reputable cuevas recommended by locals. Count the money in front of the clerk before you leave the counter.