Mexico City is best in late autumn when the air is crisp and the summer crowds have gone home. You get clear skies for walking through the murals at the Palacio de Bellas Artes and cooler temperatures for spending hours digging through the stalls at La Ciudadela.
When you're ready to pay for the $1500 trip, you can use the Citi Simplicity® Credit Card. It offers 0% for 18 months on purchases and balance transfers from date of account opening. This lets you spread the cost out over that intro window on purchases rather than paying it all at once.
The 0% intro window is a deadline, not a gift. If you still have a balance once those 18 months are up, the bank will start charging interest on whatever is left.