Yes! Book your villa as soon as you can! They tend to go fast. Yeah at some point you'll be pot committed and have no choice to book a flight regardless of cost but you have easily 6 months to watch airfare. Look for the price you want to pay and when it gets close, pull the rip cord! I don't think you'll have any issues though.
Spirit? Hmmmm, I wouldn't but they can be cheap. Once booked 10 guys on Spirit from DTW to LAS for a bachelor party. They called us less than 24 hours in advance to let us know they were cancelling our flight and had no alternatives for us. (ie. no other flights to replace the one they were cancelling). We were on our own to book ourselves a new flight with less than 24 hours to spare. Cost per person was $400 more last minute like that and Spirit wasn't about to compensate either. Oh, the reason for the cancellation? They had NO PILOTS to fly the plane!!! Come on! Do your research on them. If they have to cancel, it's not like they have spare planes to get you there. Same if you miss your flight. Options are very limitted. You get what you pay for as the saying goes.