Wow, that will be quite a drive. I can't offer help on public transportation(buses) because I don't their routes from La Romana but I am sure you can catch a bus from La Romana to Santo Domingo, and then tell a taxi driver to take you to the area where they have the buses (smaller buses by the way) that will go to Boca Chica. Taxi from Santo Domingo to Boca Chica should be about 15-25US, I personally wouldn't pay more than 20US because I take the little buses back and forth from Santo Domingo to Boca Chica and costs less than a dollar, but I just can't remember the location to give you. By car I would say 2 hours is a good estimate from the airport to Boca Chica. I think the highway you take is number 3 and it runs from La Romana to San Pedro de Macoris, it runs all along the coast, and then you can get off into Boca Chica. If you are renting a car, after you pass through San Pedro, Juan Dolio, and later you will see a Boca Chica sign and you turn off the highway and enter into Boca Chica. I don't recommend driving because it is very hectic there and speed limits and laws of the road, is all about defensive driving. You will be cut off, very few signals are used, and have to avoid little motorconchos/motorbikes with 2-4 people on them or loaded with produce/supplies, etc. I would assume if you took a taxi from La Romana it would probably run you at the minimum, since you are tourists, 60US after haggling, but more than likely they would want about 75US give or take 10 dollars. I am sure others will help you out more than what I can but this is all the advice I can give as accurately as possible.
dale7(Howard)