Are you looking to cut costs? Or are you looking for luxury?
Either way I will give you a plan so you can feel safe and somewhere inbetween. Get a cab to Zona colonial, get them to drop you off on EL Conde at the top end. About 50mtrs from the cab rank there is a place called Casa Conde, it is very modern, clean and welcoming, yet basic, but cheap. Stay the night there. In the morning get a cad 50mtrs away to Gomez to catch your coach. I wouldn't pay much attention to the hours as they put extra coaches on and they don't appear to stay to the time table (if my experience is anything to go by) and so expect the 2pm to be leaving at 2.45 and the 4 to be leaving at 5pm etc etc. But the last one is 4pm and if they want to they will leave at 4pm. In the Casa Campo they have a free computer with internet access, you can plan the next day from there.
I only recomend Casa Campo as it is in the middle of the Zona on ther main street and you will find it more welcoming and familiar with other pale faces than if you head off up to Gazcue or even if you went to the malecon, it isn't that reassuring at night.
Now you just need to figure out which is worth it.
Best prices to stay a night in Santo Domingon = Cab RD1,400 into Zona Colonial.
Night in Casa Conde = RD1,400 - RD1750 (the single rooms are tiny ad so you may opt for the slightly larger at RD1750).
Meal and a couple drinks RD1,500 (if you just have a 'few drinks', my account would realistically be about RD3,500 for food and drinks for one night not going mad).
Cab to gomez in the morning = RD250 (shouldn't be more than Rd200 but lets not get into that).
Breakfast = RD500.
Coach ticket = RD400.
Once in Bavaro your cab to your hotel = ?RD1,500 (for arguments sakes)
Total = RD6950, $160US at the cheapest end.
Personally, for the sakes of the hassle and even having to mess around with the capital, I'd be heading straight over the Bavaro, screw a night in the capital.