You can ride yourself anywhere from Custom House. I was in Trinidad North and drove down there wth my powerchair, but even if you are in Trinidad South (furthest away) it's a nice trip and not too long. Depending on when the internal bus shows up, you can even beat the bus to the room!
You can't take luggage on the internal bus. Therefor, at CBR you can let bell service deliver the whole thing (which I did, they were there about 10 minutes after I got to the room, also with my checked luggage) and walk/bus yourself to the room or let yourself be brought to the room with one of the many carts they drive around. On this you can bring your luggage as I was told. They've got carts (think it was a van? Don't know for sure) that'll take a wheelchair, I was told, but when asking -couldn't believe it- about it taking a powerchair, they seemed to realise they could take a manual chair and that's it. No prob! I just drove myself back to Custom House when it was time to leave and all of my stuff was there waiting for me allready (had bell service pick it up).
The pathway to and from Custom House is paved and easily to spot. While you will have to cross a road, it's an OK cross. Proper view, warning signs for the cars etc. Every bus I've encountered (or while riding the bus and somebody else wanted to cross the road) stops and I only run into 1 'tourist' car that was doubtfull for a moment if they should break (yes, there is a pedestrians thingie, how do you call them, the thing with the black-white stripes on the road) and then did break with enough time and room to spare.
Don't worry, you'll be fine.

If you've got any worries or problems, just ask for the manager Cedric. He was exceptional when I was there and really geared to making any stay a good one.