Traveling South America Tip

Friend of a friend is headed to South America. Asked some light advice on the section between Iquitos and Manaus. I riffed. Here it is.
Dear X: Iquitos to Manaus can be done by riverboat or speedboat: Riverboat is better. You get to stop at the San Luis Leprosy village--there are three in Peru, I think--as well as at several other ports that are pretty interesting, including one where Hassid's grow tons and tons of marijuana. That riverboat will take you to Santa Rosa, the Peruvian town just across the river from Colombia's Leticia--or Leticia itself--which is connected to Brazil's town of Tabatinga--as in across the street. That used to be a wild area, a place where International crooks hung out because if, for instance, the DEA had a warrant for your arrest in Colombia, you'd cross the street and be in Brazil and they'd need a new warrant. Or canoe 200 yards and be in Peru. First time I was there I must have met 10 guys I'd worked with at the Feast of San Gennaro in New York--all wise guys on the lam, living high. It's still pretty cool.
From Leticia you take a boat to Manaus--it's about 6-8 days, depending on the boat/the river. Again, if you have the time, much better than a plane. Not expensive. Rent a cabin if you can swing it. It will be simple, not some fancy-dan cruise ship cabin, but it will mean that you get a couple of chairs to sit in and a place to stash your stuff without having to worry about it. If you just get hammock space you're sort of anchored to that because there will he a couple of hundred people around and the moment you leave to go to the bathroom or take photos or get a beer, someone will be taking your stuff. So yes, cabin is good for the couple of hundred bucks it will cost, even if it's simple. 
You get time in Manaus, head up the Rio Negro to where it's not developed and you'll have a grand time.
Key to South America: Outside of Colombia, and eastern Brazil, much of the continent is a matriarchy. It may look like the man is the boss but if it does that's only because the women allow that. In truth, mothering skips a generation, so that 16 year old daughters have babies, the grandma takes care of them. Grandma, 32-35 years old by now, is finally ready to quit her dancing days and raise kids. So she raises the grandkids in a way she never raised her own. 
That relates to you in this way: Make friends with grandma, any grandma you run into and since she is the center of her family's universe, all will be well with you in regards to that family. That's important, particularly when your sister--who will be traveling with you part of the trip--is involved: You're a gringo and might not read signals right, so you might over react to a man and if he loses face he'll have to challenge you. But if you've made friends with his mother, she'll intervene and solve everything with a couple of beers instead of blood. 
Most of where you're telling me you're headed is not very macho. People won't stab you or anything. Bets off in Lima/Bogata/Santiago, of course: Those are international towns peopled by a huge cross-section of population. But outside of the big cities, nobody is going to hassle you. I can't speak for Argentina because I've never been there--some politician 12 years ago filed something against me as editor in chief of High Times mag and I wound up getting 22-years in absentia, so I won't be visiting there anytime soon. Seems his kid was reading one of the issues on the internet where I was editor and he laid a charge that I was, as editor, pandering drugs to underage kids. Crazy but real, and while the US refused the request for extradition, Argentina went ahead with the trial and it turned out I lost. 
When you get closer to leaving, push. I've got some good info and am more than willing to share it with a friend of Phil's. 
You're gonna have a great time.
Peter G