I flew back from Acapulco some years ago (on Princess) and had a change of aircraft in Los Angeles. Other UK bound passengers went via other US gateways. A direct flight shouldn't take 17 hours so I guess you will be stopping off somewhere en route. It's not really a major hub for international flights so unless you go on a P&O chartered flight a stop off is almost certain. Even then, they tend to use smaller aircraft so a refuel stop is quite likely, at which point you get off and stretch your legs. Have a look on www.expedia.co.uk to get an idea of who flies where and approx flight times. Hope you aren't going loco by the time you get to Acapulco!! I'm sure you will have a great time.
Refer to my responce to a question posted by Mr Keith Barley on March 26th 2008. I think this will answer your question. With regards to the flight time, it does take about seventeen hours to get there I know because we have done it. Trouble is, the planes have a refuelling stop on the way in Cuba or Dominican Republic, before continuing to Acapulco.
We have just returned from a panama canal cruise just over a week ago. we also flew to acapulco which took 13 hours plus a one hour stop over at dominican republic. it didnt feel like thirteen hours as most of the time they are coming round with meals or complimentery drinks. there is also plenty to watch on the tv and if you are lucky you may get a couple of hours sleep. but we were suprised how fast it went. unfortunatly you dont get a lot of leg room on the flight we were on which was thomas cook. dont let it worry you too much as i'm sure you will have a lovely holida.