(Caracas is the capitol of Venezuela--nothing to do with Columbia.) I would not go off on my on there. We were there a couple of years ago and took an all day tour into town--visited the capitol bldg, did some shopping in town and went to the glass factory. Part of our tour was lunch in town at a very nice restaraunt which was very good.
It is a major city with a population of several million. The traffic can be bad but it is worth seeing. Again, I would not go off on my on, if for nothing more than getting back to the ship on time. Remember, if you are on a ships tour they will wait if the tour is late. If you are on your own they won't have any idea where you are and will not wait.
I hope you do take a tour as it is worth seeing. Anyway, if you don't like it, you can always say--hey, we went. Better than saying--we didn't get off the ship.