i've stayed there before and i have only GREAT things to say about it. You will enjoy. it's safe, clean, has water, power, fully furnished. you will be close to everything and anything in costambar. Jenny's market is a wonderful supermarket and you will find everything you need there for good prices.
also, the taxi rates across the street are NEGOTIABLE!!!! don't pay full price - EVER. one way trip to the city is RD$200pesos. if you are going into the city don't ask for the price, just have the 200 pesos ready (exact change) and hand it to the driver - that's it!!!! if you start asking for rates they will charge you whatever they want!
if you need a rent-a-car (short term or long term) see Amado across the street from Jenny's Market. There is also an internet cafe next door to Jennys that offers free internet friday's for happy hour 6-9 pm.
When you go down to costambar beach visit pascuals place (tiki hut like restaurant) and say hello to Cesarina - she is The BEST hostess in town!