Our hotel was located in the historic centre, and we had dinner at a hotel under the same management which was just round the corner. On leaving, we turned right, as we wanted to see Plaza Bolivar by night, but the hotel staff told us it wasn't safe. We went anyway, as it was a couple of minutes' walk away and there was no one about, but we kept a careful lookout, and quickly returned to our hotel.
Half an hour later, the lady from the other hotel knocked on our door - she had come to check that we were back safely.
Although we saw nothing alarming, her concern suggests that there is a very real need for caution.
Living here, I thought that health warnings would be the same as in Paris...Well, the centro de salud (health center) of Ciudad Bolivar has different approach concerning malaria medecine. Here, they don't recommend taking malaria preventive medicing (apparently making it impossible to detect in tests) and won't give it to you (u can beg, cry, negotiate...).
Note that within the European union, countries consider ciudad bolivar as a risky area (germany, holland...) and as non-risky (us, france). I've never heard of Malaria in ciudad bolivar but yes, it seems like my tour guide caught dengue (and no...u can't preven that from happening)
So, if you're concerned, want to take those pills..do the necessary before leaving your home country.
You should be carefull like anywhere else but if you decide to go for a romantic walk after dinner, I would recommend to be carefull and walk in an area you've seen under daylight. As much of the hotels are located in this beautiful barrio, you should know that certain areas are unsafe even for people who have lived there all their life (my boyfriend's family is an example). The bottom part of Calle Concordia is full of drug dealers and their addicts... even taxi won't stop around there.
If you get lost, try to orientate yourself with the river. Get close to it (probably means walking downward...) and call a taxi.
Personally, i love walking around there cause people put their music outloud, chat for hours on their porches with family, friends and neighbors. It smells food and life around there.