Venice draws its most attention from tourists during the peak travel months of June through September. Also, during the ten-day Carnival in February, so hotel space and elbow room are in short supply.
Venice has hundreds of hotels, hostels, and vacation rentals. However, most are rather small, and it can be difficult to find a room during high season or on holiday weekends, so it is best to book in advanced.
When you need to acquire or exchange US dollars into Euros the easiest result would be using your ATM or your local bank before leaving home. You’ll almost always get a better rate from an ATM than from a bank, an exchange counter.