I'm flying down from the UK for a week in BA shortly and was wondering if anyone could answer a few questions and possibly provide any tips.

Q1, Can I use the USD for taxis, restaurants shops etc?

2, I saw Groucho's post re Uber. Should Uber not be used at all, especially from the airport? If not how should I get a taxi from the airport? Is it best to pre book?

3, I was thinking of taking the fast boat to Montevideo for the day. I noticed that it is priced in $. Is the Pesos? The price is on the high side.

4, I'm staying in San Telmo. Is it safe to walk about here and BA in general? Is there anything or any area best avoided? I like to wander about but don't take silly risks.

If there's anything else I should be aware of I'd love to hear.

TIA

G