Expect VERY high pressure. Lots of outright lies. They have answers to ANY objection you may try. They make these offers to appeal to your (and my, and everyone's) desire for a bargain. A 'deal'. Frankly, greed. They make it sound all so friendly. 'Sales talk', but they fail to mention that it happens very early in your stay, so that the legally required rescission (cooling off) period (which may not even get mentioned) will be expired before you can find the instructions and get to a Mexican post office to mail a letter saying you want out.
Personally, I wouldn't go. But that's me. If you should decide to go, get the address to mail a rescission letter- and possibly even write one before you go. Find the nearest PROFECO office. That's the Mexican consumer affairs office that deals with timeshare sales. They can help with a rescission.
Cancun is beautiful and there are lots of great activities, but you don't want your vacation to be tied up trying to undo a $25,000 (or much more) mistake.
Jim