First of all, is the procedure something the insurance company never approves, or is there some reason they didn't approve it for you? If it's the latter, I've read on this site that the lapband company will fight insurance battles for you. I can't remember the name of the website you need to check, but perhaps someone else can supply the name for you.
Secondly, if insurance won't pay and you are able to borrow the money, I think you should give serious thought to doing it. As women, we tend to take care of everyone else first and seldom get around to taking care of ourselves. You're not being selfish by wanting this surgery. In fact, it will be better for the entire family if you're happier and healthier and able to live a longer life with them than you might have without the surgery.
Thirdly, I've read of many people who have gone to Mexico for the surgery and have been very happy with the experience. But I've also read about people who have had the surgery there, have had complications upon returning home, and have not been able to find a doctor who would treat them due to liability issues. If it were me, I'd have the surgery closer to home where I had easy access to my doctor.
I wish you all the best as you make the decisions that are ahead.