Even though I speak Spanish with my Chilean classmates and the family I stay with, I actually used a lot of English this week while I was traveling. Our scuba diving guide in Pichidangui spoke excellent English because he lived in the United States when he was younger.
I also spoke English with the Dutch exchange students with whom I traveled to Valpo because they speak English, but I don't speak Dutch! A lot of people asked us where we were from when they overheard my friends talking to each other in Dutch. It's not a common language here, so Chileans don't recognize it the way they would recognize English.
Everywhere in Chile uses pesos, although it's easy to use a credit or debit card at most places, which saves us from having to carry too much cash around when we travel. It was a good thing I stocked up on peso coins before heading to Valpo, though, because all the buses and cable cars there use them instead of the pre-charged bip! card I use in Santiago.
Water costs pretty much the same (about $1 US) everywhere I've traveled in Chile, although you can also drink tap water. I've been making a lot of tea myself. Thankfully, tea bags are also cheap here (about 800 pesos or a little over $1 US per box).