I have done both...rent a car for the week and for just a couple days.
I would do the couple days again. We were close to the airport though for a cheap taxi ride. If you are far I would def. rent for the week.
We are vetrans of driving in St. Lucia and couldn't navigate our way around Barbados to save our life. Road signs are not really something you'll see much of and maps are mostly outdated. In one spot the road was closed and actually diverted through someones backyard!!
Hubby usually does all the driving and he's good at it. One day I just wanted to go up the street, short drive to the store. Well I side swipped a hedge almost knocking the side mirror off before I even got out of the resort and barely missed a head on collision with a full size bus. I'm not allowed to drive anywhere on the left anymore.
There is a BajanNav download (google that) for your GPS. Unfortunatly we couldn't figure out how to pull it up as we just bought the gps and left instructions at home. LOL
Hope this helph
Renee