My advice, make sure you have insurance. You can get it at the parts store (can't remember what it is called, but between Cabarete and the Texaco gas station...bright yellow building with usually a few people standing in line holding cheap Chinese parts that need replacing). It was pretty cheap. Like $25 bucks for a year. Bring your title and an ID. It takes a couple of weeks, but they will eventually give you a card to carry with you. It certainly won't cover the actual costs if you actually hit someone\something, but you will at least reduce the risk of being hassled\extorted if something minor happens.
I either rented or owned a bike in Cabarete for 7-8 years, and the only time I had a problem was one year when I happened to be cruising through Sosua when they were doing a helmet crackdown. I (and like 200 others) got scooped up in the net. Their courtyard was full of bikes of all different vintage and functionality. Sea of bikes.
I wasn't wearing my helmet, and got what I deserved. Had to take a motoconcho back to Cabarete to get my helmet (there just HAPPENED to be one there waiting for me!), and I did get a ticket, but I was able to work it out right there at the police station (it was complicated, I tried to pay the officer that was holding my bike, but he refused to take it, said I had to go to city hall, but city hall was closed, so after some discussion he just let me go, and again, refused to take any money, and I tried and tried to give him something, very professional).
And remember the right-of-way rules of Cabarete. Yield to anything bigger than you. Period.