If you want to go to the desert in the summer, you should have no difficulty using II, though WKV usually has less inventory than SDO and the Marriotts (which are reportedly very nice). Normally, I'd advise using Ongoing Search to capitalize your chances of getting WKV, but if you do that, you lose the ability to upgrade to a larger unit. IOW, if you list a 2 bdrm, you have to surrender a 2 bdrm.
If you do Instant Exchange, you can select just one side of your unit to exchange (e.g. the studio), and then search. If you see something listed, you can book it, even if it's a 2 bdrm. You can often get 2 2-bdrms for your one 2 bdrm lockoff, especially for low season, such as desert properties in the summer.
Another very attractive option is to book an II "Getaway." These are simply excess inventory that they sell for cash -- no exchange required. You can often book a 2 bdrm for far less than the cost of MFs. I'm talking $300-500 for Starwood and Marriott 2 bdrm villas. (You can also book Getaways for family and friends by paying an exchange fee.)
IIRC, you usually start seeing summer desert weeks Getaways in the Feb or March prior, so you have time.