Vegas is good fun, and you'll be ready for a slice of normality after 4 days.. You don't need a visa, you need to get your ESTA which you do online before you leave. I went a couple of years ago, go to old town vegas as that's where the cheaper casinos and bars are. Play some black jack and have the local old ladies teach you how to play properly, it's good fun. They say you get free drinks whilst you gamble, and yes this is true, but unless you're a high roller who tips big, you wont be inundated with service. Be careful at the bars in the larger casinos, I paid $100 for 4 beers and 4 shots of jaeger in one of them. Hoover dam is well worth a visit, as is the grand canyon.. The less said about winning back your ex with a trip to vegas the better, April is a long way away, a lot can happen between then and now. Airlines don't like changing names on tickets either, and I'm pretty sure it's against the law in the US to do so.