Are you renting a car? Suggest sticking with the big brands, even though they are still just franchises. Also if you're driving around keep a second wallet, with your license and just $20 or so cash, have been pulled over a few times and police seem to lose interest if they can see you don't have much cash.

Have driven the length and width of the DR, outside the cities driving isn't too bad, get into the capital though and it gets a bit crazy, find it best to drive there assuming anyone else is about to cut you off, and their use of indicators is optional.