It might be easy to assume that San Juan, Puerto Rico would be a cheap destination, since it’s not really known as a wealthy place, but unfortunately this is still quite expensive. The location in the Caribbean gives it ideal weather for cold-weather people during winter, so demand is quite high, even away from the beaches.
Hotels in particular are unusually expensive for a Latin American capital city, as are hostel beds. Those who look carefully can find some very cheap one-star hotel rooms, but expect the quality level to be very low. The proper 2-star and above hotels charge resort prices, even during the off season.
Food is also fairly expensive as long as you are in the main tourist zone. Some street-side options can help to keep your overall meal total down, but sit-down meals, especially at hotels, will be more expensive than most of Mexico, by comparison. Drink specials can keep entertainment costs down a bit if you find happy hour deals.