The ending (SPOILER)
I normally hate it when the writers/directors intentionally leave the ending wide open for interpretation like that (Brokedown Palace - which one was really guilty? Both? Neither?, or No Country for Old Men - did he kill the guy's wife or not?, 2001 A Space Oddysey, the whole *($@(*$@# movie was open for interpretation).
But I thought that the girl getting away was an interesting touch - what happened to the plant seeds (viruses?) she was carrying? Did all of Mexico end up getting overrun by these plants thanks to one stupid tourists?
And the two greeks who showed up - so they showed up, so what? What does that mean? That the Mayans would have been so stupid as to let them get away and go get help, or that two stupid greeks would have made a bigger difference than the 6 reasonably intelligent people who showed up before?
I sound like I'm being sarcastic and I partially am, but my point was that though I normally hate ambiguous endings I kind of felt like the way they ended THIS movie "worked".