I bought a tamron 28-300 a couple of years ago for my sony 850 and practically haven't taken it of the camera since..........I think you'll really like the lens for it's versatility.........you can buy them used for less than $300..........

I've been to peru and Bolivia and learned from local guides that a lot of native people in rural areas don't like to have their picture taken.........they believe a printed photo of them can be cursed or even be burned and cause their soul to be stolen..........so you can't just walk up and take their picture.......a longer lens is much more discreet......I use a tamron 28-300 and gave been very pleased with the results..........enjoy your trip........it's an amazing continent