Is it cheaper to book buses in advance?

Rarely. Booking at the station 24 hours in advance is usually the same price and provides more flexibility.

Should I bring US Dollars or local currency?

Bring crisp, new $100 USD bills to exchange at unofficial rates in countries like Argentina, but use local ATMs for daily needs elsewhere.

How to budget for a one-month backpacking trip in South America

You need to budget between $1,800 and $2,500 USD for a one-month trip, depending on your pace and region. This covers hostels, local buses, two meals a day, and mid-range activities.

Account for regional price tiers. Budget $40–$50 per day for 'cheaper' countries like Bolivia and Peru. Increase your daily budget to $70–$85 for 'more expensive' destinations like Chile, Argentina, and Uruguay.
Prioritize overland travel. Internal flights in South America are expensive due to limited budget carrier competition. Dedicate 20% of your budget to long-distance buses; use 'cama' (full-recline) seats for overnight journeys to save on a night of hostel costs.
Calculate a 'cushion' for activities. South America is activity-heavy (trekking, tours, park entries). Set aside a flat $500 lump sum specifically for bucket-list items like a Galapagos cruise, Machu Picchu trek, or Uyuni Salt Flats tour.
Use local ATMs strategically. Use a bank card that refunds ATM fees (like Charles Schwab) because machine fees in countries like Argentina can reach $10 USD per withdrawal. Always carry a secondary stash of $200 USD in clean, crisp bills for emergencies.

Is it cheaper to book buses in advance?: Rarely. Booking at the station 24 hours in advance is usually the same price and provides more flexibility.
Should I bring US Dollars or local currency?: Bring crisp, new $100 USD bills to exchange at unofficial rates in countries like Argentina, but use local ATMs for daily needs elsewhere.