omg... I know this is part of the experience but this will only be my second time in DR and when I'm thinking big bus I was thinking of something like a greyhound bus. Matilda, is the first picture of the purple van what you are referring to as the guagua that goes to Boca Chica? In that case I'll either take a taxi or use the hotel shuttle that goes to Boca Chica!
LMAO............
Don't panic. The first pic is a typical guagua which will scoot you around town and they also have routes that can take you to Boca Chica. The second pic is a larger, nicer guagua that goes to Boca Chica, and other cities. There are these "larger guaguas" a little nicer with curtains, doors that close, and A/C.
To the best of my knowledge there is no "big bus" Greyhound type that goes to Boca Chica. I am thinking when you say "big bus" you are talking a bus you can buy a round trip ticket. A bus that has designated bus stops. A bus that actually runs on a schedule. If I am correct you can't get to Boca Chica on your type of "big bus".
It is not that difficult to take the larger guagua like Matilda mentioned to Boca Chica. This being your second trip to the DR I don't think it would be a wise thing to do. First you would have to get to Parque Enriquillo. Now you need to find out which larger guagua is the one you need to take. As Matilda mentioned the larger guagua leaves when it is full............ so you sit and wait. Your return trip will be a repeat.
What hotel will you be staying at in SD? Will you be going to Boca Chica solo?
If you want to have fun and make it easy on yourself I would suggest taking a regular taxi to Boca Chica for around $35. Leave Boca Chica around 5pm and take an express guagua back to Santo Domingo. To me taking the guagua back to town always seems easier.
Let me know what you think?