Take good mosquito repellant with 95%DEET (definitely keeps the mosquitoes away but long time use makes the men sterile according to some studies). I would not bother with anti-malaria drugs because of their side-effects (they can make you feel ill during your whole trip). DEET that makes you sterile, anti-malaria that gives you nausea? One of those nasty flu viruses going through the Canada and the States is way more serious.
My suggestion, do go to the local camping outfitting store and get that 95% DEET mosquito repellent. You'll stink like hell to those nasty mosquitoes that can be annoying wether they carry malaria nor not, and you can still reproduce very successfully unless you rub it ALL over for at least two consecutive years. You will not get stung by those nasty little suckers and you'll feel safe.
But then again, look at the numbers. According to the cdc.gov (Centers for Disease Control and Prevention), there have been 17 reported cases. 16 during Nov 3-16, 2004 and 1 patient that returned Dec 20, 2004 (details missing). All recovered, none died. http://www.cdc.gov/travel/other/malaria_dr_2004.htm
All were in the area of Punta Cana (east coast). During that time some 100,000 tourists passed through that region alone. That would have given you you a very small chance of catching malaria. Since that time, there have been no more reported cases to my knowledge.
But more relevant to your concern, no cases have been reported from either the South Coast nor the North Coast.