We didn't have a car. When we were dropped off at the custom house, they tagged our bags. Then after checking in, we went to the bell services counter and they took us and our bags in a van to our room. When we were ready to check out, we just called on the telephone and they came to pick us up within 5 - 10 minutes-- and I think it was as busy check out time so this wasn't too bad.
From the standpoint of being close to Custom House and OPR, Aruba was a decent location. It was a little longer walk to OPR than Jamaica, but we were closer to the Custom House than Jamaica is too. Barbados would be even closer to the Custom House but maybe a little more of a walk to OPR. I must say we didn't mind the walk. The grounds are beautiful. We left CBR for the Wonder where we did a lot of walking on the ship to.
There is an internal bus that goes around the 'islands'. And depending on what you need from the Custom House and the time of day, they might bring it to you. We added a night to our package, so we had to check out and check back in after our first night. They offered to deliver the new keys to our room. The only problem was that we were leaving for the park earlier than they could put us down for the delivery. So, I just walked up to CH the next morning and it took me not quite 10 minutes from Aruba. And it was a beautiful walk on the Lake and then I cut through Barbados.