I and some friends are taking our vehicles from the US to Honduras. Once we get to Honduras, we're golden. However, navigating the space between San Antonio and Copan Ruinas is tricky. I need some guidance on a route. Which borders should I cross. Which cities should I stay in overnight? Which roads should I take?
The Pan American Highway is probably the most popular route.
Mexico and possibly other countries require insurance from an underwriter in that country. It will probably be a lot cheaper to arrange that before the trip.
It would be worth checking to see if it is unsafe to travel in certain areas, and at night. In Nicaragua, for example, there have been recent cases of unofficial roadblocks on the main highways at night, for the purpose of robbery. If someone you meet suggests that you avoid an area, it might be a good idea to take the advice.
You can check the State Department travel advisories for the countries you plan to go through. They can be overly pessimistic sometimes, but they do give some important information, particularly on recent criminal trends and dangerous areas of a country.
In Mexico and other countries with a large illegal drug industry, it can be dangerous to drive around the countryside in sparsely populated areas.
Despite all my doom and gloom, it sounds like it will be a great trip -- have fun!
Bear in mind that it is winter season in Central America (until late October). And while staying in the Pan American highway is probably your best bet, there's still chance for roadblocks caused by mudslides, collapsed bridges, etc.
Road infrastructure on those countries isn't exactly at the same levels you are used to.