Hi, I did this myself last year as a woman traveling alone. The buses are safe as milk; very very safe and comfortable and convenient. I sat next to local women and we conversed all the way. All the bus info for getting across the island is correct as I experienced it. I had a terrible time getting the cab price DOWN to only $30--everyone wanted tocharge me $40-$50. I finally had to walk away ,rolling my suitcase, telling them in Spanish that I would take the local bus out on the main highway for a couple dollars, instead of their cab.
They let me walk away half a block, then ran to get me and said "Ok, $30 to the bus station." Once you are get out at the bus station in Puerto Plata, you can just walk to the main road and wait for the next local bus (65centsUS). they come along every 15 minutes or so it seems. Very good service, one fare no matter how far you are going locally; the hotel was at least 6 miles up the road but it only cost me 65cents. After I stayed there a week I asked a cab driver what he'd charge back to the bus station: $25 was his answer.