You should think about what kind of Dominican culture you want. What you see in the Colonial Zone can vary within itself, and of course, it varies outside.
I'm 27, and "party" regularly. Some of my Dominican friends are more Westernized then people I know from Canada. Not that I care, but you might have seen this too. Don't think that what you see in la zona colonial ISN'T Dominican culture. If you want to kill goats in the campo, I would be hard pressed to find a person that could direct you somewhere to go.
Moving on.
I've lived in Gazcue, and Ensanche Julieta. Both are fine. I don't drive, so my criteria was to always have a supermarket near. In Gazcue, it was a tiny Cadena, in Julieta I have La Sirena and Bravo in walking distance (along with Bluemall and Acropolis),
You couldn't pay me to live on the other side UNLESS I happened to get a MUCH better job there. Traffic is terrible if you work on this side, and I hear about it regularly from co-workers. Of course, you might see more stereotypical Dominican "culture" over there, but I'm not an expert.
When I worked in the office regularly (in Naco), I would taxi from Gazcue (which was stupidly expensive). Now I take a bus for 1/6 the price, once a week, and its great.
I actually walk home from Naco to Julieta on Tuesdays; about 30 minutes. It's stupid hot, and I have my bag and computer, but its the only exercise I get (and unlike some people here, I could care less how I appear to others).
I made a map (how sad). The red dots from left to right are (1) Where I live now (2) Work (3) First apartment.
When I go out, its basically to la zona colonial, and since most people I know drive, its not an issue. I probably wouldn't have walked home from la zona to Gazcue at night even when I lived there. If you don't have friends that drive and live near you, taxi's are an okay way to go, I did it 2x a day for almost a year. When I consider the money I save now, its insane.
If you want to be near the university, just live around it, I'm sure there are pockets that fit your "barrio" criteria.
Tell us more about the type of person you are, where you went in la zona colonial (or other places) and we can tell you more.