Jump in a publico (anything on 9 will be going to 12km so you cant go far wrong), it is Duarte after all, you are not going to get lost, 25 pesos. Just tap his shoulder when you want out! simple.
If you are a bit unfamiliar with publicos just flag down a conchisto, 40pesos will get you to 12km
But if I was unsure or paranoid or clueless I would probably take the 12 minutes needed to walk it.
I remember the early days in the city, a bit freightening to get involved in the public transport and so ended up taking taxis everywhere. Start using the publicos around the capital, not the guaguas, and you will be able to navigate it entirely within a few weeks confidently, know the numbers of the cars and which to flag and which to wave on by. Good luck.