Dutch and English are the two main languages that are spoken here. However, Utrecht is a large city, and you'll hear many other languages, such as French, German, and Turkish, just by walking around (especially in the train station -- the largest one in the Netherlands)!
Like most countries in the European Union, the Netherlands uses the euro. One euro (€1.00) is worth a little more than one US dollar ($1.14, right now). The Netherlands removed one- and two-cent coins from circulation in 2004, because they cost too much to make, so their lowest coin is a five-cent piece (a nickel, to us). So, if you pay for something in cash, they round the price to the nearest five cents.
It's safe to drink water from the tap in Utrecht, so I haven't needed to buy any bottled water! I think I remember seeing it for a couple of euros at a train station, where everything is marked up, but it would probably be around one euro at a grocery store.