I was not able to find exact number of tourists visiting Boca Chica yet. Here is what wikitravel.org says about the town in general:
'It has a population of around 70,000 and is once of the largest towns in the Dominican Republic. Boca Chica was originally a fishing village but has evolved into a tourist destination due to its stunning beach. The beach at Boca Chica is sometimes referred to as the largest swimming pool in the Dominican Republic as it is well known for the coral reef that makes the water so calm'
Also there are more than 5000 reviews of different places in Boca Chica on TripAdvisor.