If you're diving with coconut tree, you don't absolutely need a computer. The profiles on all the dives I've ever done with them are very safe and conservative. You can use the PADI wheel to plan the dives by asking the DM what his/her dive plan is and plugging that info into the wheel, then calculate your own PG info. You'll just have to stick with the depth/time of the plan. They're all easy multi-level profiles in which the last third of the dive is very shallow, often 10-15 minutes at 20 feet. The wheel is a good tool; maybe the most useful thing I got out of AOW was learning to use it.
You can decide about the other stuff; you already have a wetsuit, correct? That's the most important thing to avoid renting due to fit/comfort issues. CCT is a dive rite dealer so I believe their rental regs are dive rite, very decent quality, and my guess is that their prices will be comparable to deals you'd get in the U.S. if you wanted to buy there after renting to check out the gear. There's also a mares distributor on the island; I had an old pair of fins fall apart on a dive trip, and bought new avanti quattro fins for less than what I would have paid in the states. That's unusual for an emergency purchase.
A LDS "rent to own" deal is only good if you really want the gear and the price is right.