We've been to WJL a few times, and are now becoming owners through resale. Great place, but damn expensive. As soon as you walk in the door you start bleeding money.
The AI is worth it if you drink and eat A LOT, otherwise it's not. They used to have a discounted AI rate for RCI ($75 instead of $95 in 2004), but not any more.
The driving is fine. We always rent and drive from Hewanorra (the main airport). Car rental is expensive, but cheaper to do that and purchase groceries than take AI.
The 1-bedrooms are really for 2 adults. The sofa is in the open (no-AC) area with birds, bats, etc. They will upgrade you for a (sizeable) fee, or if you're going out-of-season (you didn't say when you're going) they might upgrade you for free. Be nice to them, and they will be nice back...
You will enjoy the place, especially the water sports. The beech is bigger now than it used to be.
Make sure you go to the Jump-Up in Gros Islet on Friday night. Just don't carry any valuables, and don't stay too late.
Have a great time!