I have Garmin tracks for most of the DR. I have them in Trackmaker format. If you are not familiar with this program go to their website and let me know if you are interested. The website is
GPS TrackMaker
The basemaps are useless. They have road that don't exist, missing major roads, and are off by miles in some places.
Have you considered getting the upgrade for GOOGLE EARTH? Its about 25 dollars US and allows you to trace and download tracks from satellite data. The detail is constantly being improved and most major cities you can see down to the street level. It give basemap-like representation of roads (which are also off by miles). The advantage of this is that you can actually "travel" your route before even coming here, become generally familiar with the route/terrain, and most important, navigate through towns/cities. There is no guarantee of this since many towns have one-way roads in and out of the city but with the absence of signs in most cases, you can "dead-reckon" through most places. There is always stopping to ask directions too
Hope this helps
Buddy