Amazon.com has a book about driving the Pan American Highway through Central America. The book was promoted around 20 August 2006. No, I don´t recall the author or exact title, but it should be a snap to find.
Many years ago a Nicaraguan buddy and I drove from Los Angeles to Masaya, Nicaragua. We had lots of trouble with the police and customs, mostly in Mexico. We tried keeping a record of the bribes we were paying, but after the second day we gave up. It was simply too much of a chore. The motor froze up twice, causing unexpected expenses.
Some of the things I learned were:
1) Wad up one dollar bills and keep them all in the same pocket. This permits you to pull out one-two-three dollars without opening a wallet or otherwise exposing your cash. This was very handy when paying small bribes. Once a man has seen ten dollars in your hand, a five dollar bribe looks like slim pickings.
2) In Mexico (where almost all bribes were paid), they found a unique way of gouging us. To cross Mexico, we had to put up a bond on the truck. (Let me explain that we were hauling furniture to my friend´s parents who had retired and returned to Nicaragua a few months earlier.) In theory, the purpose of the bond was to discourage us from selling the truck and/or its cargo while in transit through Mexico. The more valuable to cargo, the bigger the bond, and the bigger the commission the bond sellers in Mexico would be paid. Guess what? They first quoted an extremely high figure for the bond. Each day the amount came down until we were comfortable with the fee. It was clearly a form of legal extortion.
3) If you don´t know how to tie knots and tie down a load, learn. Before the trip, my buddy laughed at me for having been a Boy Scout. He was completely helpless during the trip when knots had to be tied, canvases had to be secured, etc. He never laughed again. Well, not at Boy Scouts, anyway.
4) Don´t drive at night unless you have a death wish. Anything you find on the road during the day magically multiples by twenty during the hours of darkness. This applies to cattle, pickups without lights, holes, pedestrians, carts, horses, etc. Do you really want to hit burro while doing 50 mph?
5) In a perfect world, you will never leave your vehicle unguarded. In the real world, there are times when you will have no choice. Don´t tell people when you will be returning. Lie. Do you need to be gone for 30 minutes? If you say you´ll return in 30 minutes, you´re giving them a half hour to burglar the truck. If you say something like, "I´ll be back in five minutes," after those five minutes are up, thieves will have no idea how much more time they have left. Another five minutes? An hour?
6) Don´t be shy about paying someone to watch the truck. Giving someone a couple bucks to keep an eye on things tends to make them your allies. If someone is getting paid, hopefully they will feel a sense of commitment.
7) I´d say the following was baloney if I hadn´t seen it with my own eyes. Every so often we´d see a local Gestapo agent smile broadly upon seeing the California plates. He´d flag us down, waddle over to us, but before he could start his "mordida" spiel, we´d thank him for stopping us and ask the way to Orizaba or Tapachula. Somewhere, anywhere. This would completely throw the policeman off. While he was still telling us which way to turn and where, we´d hit the gas and leave them there. Remember: we´re talking cops on foot, not cops in cars. We did a variation of this in downtown Mexico City. I´m still waiting to hear the sound of a .45 rip through the cab.
8) Be patient. The bigger your hurry, the bigger the bribe you will be tempted to pay. Entering at Nogales, it took us four days to clear customs. About 99% of the time was spent waiting.
9) Stay with your vehicle when mechanical work is being done. Try to establish rapport with the mechanics. A little courtesy and kindness may keep someone from putting sawdust in your transmission or padding the repair bill.
10) Don´t touch anything without the owner´s explicit consent. Picking up someone pocketknife for a better look may be the prelude to getting your clock cleaned. There´s nothing else to do around here at night, so we fight whenever we get the chance.
11) I got some great personal advice that kept me out of trouble. I was told to shut up around anyone but my friend. Many times my buddy would say something to someone that I knew to be incorrect, but I´d keep my pie hole shut. Later he would explain why he had said what he had said. And it would all make sense. It was quite an education.
12) If those two girls are still working that gas station in Huixtla, you´re in luck. If they tell you that they´ll be back, they´ll be back. You can bank on it!
13) Don´t underestimate the power of "No se habla the English" and a straight face. We had a drunk traffic cop in Guatemala convinced we had no idea what he was talking about. Even the customs police officer with us went along with the gag. We should have earned Oscars for that performance.