I like the waterproof ones from "Rough Guide" or "Reise Know How". They're tearproof, but you can still write on them with a normal pen & coloured neon markers.
Detail is good enough for most things. If I really want to do some small tracks, I'll buy a more detailed map locally.

Agree buy locally...
 

We are currently in Panama on our way south. What we've learned is to check the date on the map you are buying, buy it in country, and to ask the folks you meet. Lots of updating of infrastructure going on, new roads being built, old roads being resurfaced. But people throughout the region are almost ALL tickled to help you out, and it is a nice opening for conversation.
Enjoy!
Mike (and Heather)
Haciendolo…