It is funny how restaurant norms differ around the world.
I remember seeing a small charge on a bill in Spain many years ago only to be told that it was for the bread and knives & forks!
It seems that in BA, a charge for the silverware is the norm. Of course, 8 pesos is less than $2US.
I believe that the tax (VAT) is included in the menu price.
Andrea is correct. Everything I read seems to indicate the tips are about 10%. But I have also read that tips are expected to be in cash. So a trip to the ATM seems to be part of everyone's day!

Tips for Taxis appear to be just rounding up. BUT, everyone warns of taxi rip-offs. Longer than needed trips seem to be the most common. So, know where you are going.
Also, try to have exact change AND count it out to the driver. Seems a common scam is to 'drop' a large note, retrieve a smaller note & tell you you shorted them. This actually happened to me in Hong Kong!

Remember to advise your Credit Card company that you will be traveling. Don't want to have your card shut down because you charge something in BA & they think it is fraud.

Can't wait! Doug