Spain in late spring or early autumn is perfect. The weather is warm enough for the beach, the crowds are manageable, and you can wander between tapas bars without waiting in line for hours. You get the best of the coastal cities like Barcelona and Valencia when the rush of summer tourists has faded.
For a trip costing around $3100, you might want a way to space out your payments. The Citi Simplicity® Credit Card offers 0% for 18 months on purchases and balance transfers from date of account opening. This lets you pay for the trip in chunks rather than hitting your bank account all at once.
The 0% window is a deadline, not a gift. If you still have a balance on the card after those 18 months, you will start paying interest on whatever remains.