Yes it's safe. Just use the usual precautions like you would in any city.
Every time I see Boca Chica it's getting better and better, new developments, better streets, it's slowly moving ahead. Plus it's the best beach close to Santo Domingo.
Go take a walk down town at night, you will be fine, some good food and interesting people.
Take a look at Jims site:
http://bocachicabeach.net
This has all the info you will ever need on Boca Chica.
Make sure you visit the Colonial Zone in Santo Domingo, lots of good places to eat and a few to go dancing.
I could go on and on, just read through the site, you will find a ton of stuff to do on your vacation.
Remember, the DR is not Cancun, it's a more "real" experience when you get outside the all inclusive compounds. Bottom line, you will have a great time!