Here in Spain, the official language is Spanish, and I mainly hear that being spoken, But in Ibiza, there were lots of tourists speaking English and German. My roommate is German and he picked up on a lot of people speaking his native language.
The euro is the currency everywhere and all prices are displayed in euros. When you see one euro for example, it is equivalent to $1.10. This makes it so that whenever I'm spending money it’s not too far off from the value in dollars and if it is, it’s only by a couple dollars. I've gotten used to estimating how much I'm spending in dollars.
It really depends on the store, but if you're going to a typical local market like Mercadona, which is the most common here in Spain, a bottle of water will cost you no more than 1 euro, so close to a dollar which I found to be cheaper than an average bottle of water in the United States.
