I intend no disrespect (nor do I wish to seem insensitive) in asking this question, but the above puzzles me enough to ask anyhow.....
Is an early May week in grossly overbuilt and oversupplied Las Vegas
really likely to
ever "pull"
ANYTHING in Hawaii or the Carribbean?
It would seem to me (and perhaps I'm just plain mistaken) that such a Las Vegas week has
very little trading power for much of anything, least of all Hawaii or the Caribbean.
I own 4 weeks in Vegas. Yes, Vegas weeks will pull Hawaii and the Caribbean. The weeks we own range from the Suite's at Polo Towers to Marriott's Grand Chateau. All four of our weeks are on the strip and that could make them slightly stronger exchangers but, I don't really know that to be a fact. Also, three of our four weeks exchange through I.I. and from what I've seen results between RCI and II will vary. I won't get into the politics of my preferences between the two exchange companies.
Presently, I have an exchange into Hawaii using one of our Vegas resorts but, it's an internal exchange through HGVC and it was made at the furthest point out I could arrange the exchange with Hilton which is 9 monhts in advance. It's not really a good comparison for the OP.
As to the original question. At this point, IMO at least, you best option may be to hope for a last minute exchange. I'm not sure about RCI but with I.I., everything opens up at the less than 59 days before travel mark. Allmost all exchange restrictions are taken off and trading power for almost every resort is equal. It then becomes first come first served. Someone correct but I believe RCI calls this Last Call where in I.I. it's called the Flexchange period.
Vegas is overbuilt IMO. RCI has two resorts on the strip with Hilton's Flamingo and LV Strip. Although one could argue that HGVC LV Strip is to far north to be considered on the strip. RCI also has Wyndham's Grand Desert, which is maybe a block and a half off the strip. Then there is every other resort in RCI's book which is likely to be closer than Grandview.
However, Grandview has a very nice off strip location and the advantages of being away from all the madness of the LV Strip (some people actually LIKE to be away from all the lights, noise and action) and, they're right next to a great locals casino, Southpoint. In some ways it has the best of both worlds and I've seen many posts from people on these forums that enjoy and request Grandview because of those factors.
IMO, your best bet for obtaining Hawaii or Aruba would be to start you search as far out as possible and keep your fingers crossed. Febuary is high time for both of those locations and could be a tough trade for even the strongest exchange unit. If you're not overly particular about the resort or unit size (you might have to accept a studio unit), I feel it is possible. It just won't be easy.
With timeshare, FLEXABILITY is the key. That's something the salesmen never tell you. They ALL tell you their resort is number one and that wherever your standing is the most demanded vacation destination within that exchange company and that their resort is the most requested for that destination (sound famliar yet?). What you'll learn here is how to make your timeshare work. It's not going to be what the salesman told you but, timeshare DOES work. Most of us on these forums own multiple weeks. We own 7 weeks and hate to travel any other way with the exception of a good cruise vacation.
May is a decent time to be in Vegas. It's getting warm and is great pool weather but, I don't think it's usually hit the fry-an-egg-on-the-dashboard-of-your-car temperatures yet. We usually travel to Vegas in March when it's still a little chilly for pool weather. So you have a decent week at least and, in an overbuilt area having a decent week at a good resort means everything. The only thing you may be lacking is location and location is always a matter of opinion.
So, to sum up, the Caribbean or Hawaii may be a possiblity if you can wait until the last minute (less than 2 months) to book and are not particular (for instance St. Thomas or St. Martin rather than Aruba) and are not particular about the size of your unit. Remember, even though you may be getting a smaller unit (or maybe not), you are trading a overbuilt location in a moderate season to a high demand location in a high demand season. Even a one bedroom unit for a studio unit might be considered a good exchange with such little notice.
Keep reading and don't worry about what you paid for your unit. Many of us on these forums bought our first unit through the developer. Most found they loved timeshare vacations and learned how to buy units on the resale market and have built the remainder of their ownership on the cheap that way. IMO, timesharing is one of the very best ways to vacation and I'd hate to ever give it up.
FWIW, I'm typing this from our unit at Marriott's Ocean Pointe while looking out a picture window at the Atlantic ocean.

It's a resort we first traveled to using one of our Vegas units as an exchange. For that matter, even though we purchased here back in 2001, we obtained this very week trading our Suite's at Polo Towers unit in Las Vegas for this unit.