It's a nice, upscale condo development about 1km from center of town. Security should be good. Waters are perhaps a little dangerous at times for swimming. You could probably walk the beach into town during the day - I definitely wouldn't at night.
Transportation into Cabarete via Motoconchos/public car/guagua...
day - easy to catch one going into town
day - easy to get one to return to the apt
night - a little more challenge to find one going into town
night - easy to get from town back to the apt
Can't advise on the restaurant, haven't eaten there. Menu online at
http://www.martinisbeachbar.com
For what it's worth, there's a dance school directly across the street if you're interested in Bachata, Merengue, or Salsa.