It sounds like a good trip. Afew years ago I was able to do a sosl tour of Mexico and will pass on a few things. I traveled on 1967 r60/2 that was 12 years old. The r60 has same size frount and rear rims. iThis means only one spare think about getting someone to make up a similar setup. Also I purchased a compound called "through ride?" I was able to travel more than 15,000 mi around Mexico without a flat. A locking gascap is a must, you can add gass but you must have a cap to keep it in. Kids will steal them. The lowest compression engine that you can get helps in areas of bad gas. Older R bikes had magnetos and this means a start under almost any time,dead battery or no.lLast the dealer sent me off with a shop manual written in several languages in the hopes that I could show it to local mechanics if I needed help . good luck have fun
Stan