If you don’t have the local currency it is okay to tip in US dollars as long as you don’t pay in coins, paper bills only that are in good condition. Don’t tip with a torn, old, ripped or written on bill because it will be worthless in South America.
General Dinning: Tip 10% in cash and give it to the waiter, don’t leave it on the table. If you pay with a credit card the server most likely will not receive it. Most restaurants will charge a “cubierto” charge for the table, but this does not go to the server. If you are in a large group you will be expected to come up with the money as a whole table, they won’t allow you to pay individually like they do in the US.
General Hotels: Tip bell boys equal to $1-2 usd per bag. Leave $2-3 for maids on the table with a note saying tip so they don’t think you left your money out. For cheaper hotels, tip less.
General Transport: It is not required, expected or necessary to tip taxi drivers; in fact you don’t even need to round up the meter. However, if they are friendly, pointed out information or helped with your bags they will be more than willing to accept a small tip.
General Tours: Tip $10 usd per person for a half-day activity and $15 usd per person for a full day activity. Or 15% of the tour’s price.