By timeshare, I suspect you mean the timeshare sales pitch? Easy peasy UNLESS you booked an ultra-low rate that requires the presentation. Most timeshare resorts offer very low rate vacations that require attending a presentation, and if you don't attend, they charge you full rack rate for your accommodation. So let's assume it's NOT one of those deals, as it's probably only about 10% of bookings.
In general, Vistana is a pretty soft sell, but you need to know what to watch out for. Depending on when you arrive, you will usually be sent to the activities desk to get your parking pass. The person there is tasked with enticing you to a presentation by offering cash, credits, or discounted tickets. Just say no, in no uncertain terms and they should leave you alone. The worst thing to do is to leave them with any impression that you might change your mind. BTW - no need to be rude, and they will offer plenty of legitimate discounts and travel information - it is a real activities desk after all. It doesn't take much to get the hang of it; just remember, their objective is to get to say yes, and your objective is to make it clear that the answer is no in no uncertain terms.
If you are particularly late or early arriving, you will skip the activities desk person. In that case, they will probably call your room a couple of times with an offer for a free breakfast; they might call even if they got a no at the desk. Many people unplug the phone, but be aware that the resort also distributes information via voicemail regularly as well (like pool closures, or activity/show times). So if you unplug, I would still plug in once a day to check messages. If they get you on the phone, same thing applies as above, our vacation time is fully booked, and we will NOT be attending a presentation.
We timeshare all over, and this is pretty much standard at all resorts. A firm no takes 5 minutes, and Sheraton is pretty good at taking no as an answer. They don't want to damage their brand. For the value you get, it's a pretty small inconvenience.
We actually had a great interaction with the "sales pumper" guy at Sheraton Broadway Plantation (Myrtle Beach) a few years ago. He was an absolute blast, gave us an excellent recipe for Blenheim's and Vodka with lime, a couple of excellent restaurant recommendations with coupons, but we still didn't cave to the presentation, and he took the no with grace and cheer.