San Diego in September is hard to beat. The ocean hits its warmest point of the year around 68 degrees, the summer crowds thin out, and you get the best conditions for both catching waves in La Jolla and spending a full day at the zoo. It is the sweet spot for a West Coast getaway where you actually get to enjoy the water without freezing.
A typical trip runs about $2500 for flights, a place to stay, and a rental car or transit. Dropping that much cash at once hurts, so spreading it out helps make the math manageable. If you want to break up the cost, you can look at the Citi Simplicity® Credit Card, which gives you 0% for 18 months on purchases and balance transfers from date of account opening.
Remember that the 0% intro window is a strict deadline, not free money. If you still have a balance left when those 18 months run out, interest kicks in on the remaining amount.