Lots of advice, lots of ideas for sure. I don't envy you making the "right" choice for yourself.
As a constant traveler myself, and space always being at a premium, I'd first answer what kind of pictures you want to return with. Then let the answer dictate the tool(s) you bring with you. Just people? Just portraits? Landscapes? Distant details? This will dictate focal lengths you'll use most. Why carry a telephoto if you're only shooting exotic street?...etc.
Sounds like a hell of an experience. The way I'd go...Ricoh GR for 28mm plus flash and discreet (dinner out, sketchy places, etc). I'm an M9 shooter myself, but I think I'd take the digital equivalent of my FE2, which is the Fuji X-T1 and either a 35/1.4 (50mm equiv) or a mid-range compact zoom. I know you don't own these, so take it with a grain of salt. The X-T1 and the proper lens is very water resistant and very tough. I had my X-T1 and the 23 f1.4 up in the mountains of Hawaii and brought back phenomenal images (the only problem was lens fogging occasionally).
AND...about six or eight 16gb SD cards. Keep them in a little card wallet, mark them with a Sharpie when they're exposed. You'll NEVER be able to carry as much film as those cards, and if you decide to edit along the way somewhere (and even print and mail!), you won't mess up your original RAW files (like you might with souping film somewhere).
I know film is romantic, and generations before have traveled the world with only an M body and a single lens plus a case of film, but I'm willing to bet $$ if they had access to current tech, they'd be shooting differently.
Lastly, enjoy! Drivers and roads (and conditions) are much more dangerous in C. and S. America, so motorcycles deserve undivided attention there. Stay safe.
Hawaii (Oahu, Stairway to Heaven), rainy misty, bumpy and jostling// X-T1 + 23mm f1.4...