"If you are asked to sign a note that you are waiving the 5-day rescission (cancellation) period granted by Mexico (in case you change your mind about the purchase) that waiver is a fraud...."
I always tell people to read their contract very carefully. Look for "General Provisions" or "Notifications". For all timeshare sales operations, the customer has the right to send a letter REGISTERED MAIL RETURN RECEIPT REQUESTED within 5 business days to the address specified in the contract OR to return to the timeshare sales office and request cancellation. I always advise people to select the registered mail option, as the timeshare sales office have trained staff to salvage the sale (they will try to sell you a lesser product at a reduced price). If you reside in the United States or Canada, you CAN send the letter registered mail. It is the date the letter is sent, not the date the letter is delivered to the timeshare sales office that counts. You can track your registered letter with the United States or Canadian postal service. However, once the letter is transferred from the US to Mexican postal system, it is not currently traceable on-line. It takes up to 5 weeks for the Mexican postal officials to deliver the letter to the recipient. You will eventually receive your return receipt. Your letter should: (1) be dated; (2) contain the name and address of the timeshare sales office; (3) contain the contract number; and (4) state that you are exercising your right to cancel the contract per PROFECO. If you return to the sales office, they will request a reason for the cancellation -- do not provide a reason. PROFECO does not require timeshare purchasers to provide a reason for cancellation. If you provide a reason, the timeshare sales personnel already has a pre-prepared script to counter your statement(s). Do not return home and email the timeshare sales office to cancel your contract, UNLESS that method of cancellation is specifically permitted per the contract. NEVER telephone the timeshare sales office to cancel a contract. You must have proof of delivery of your notification of cancellation.
Here is a brochure from Profeco, the Mexican consumer protection agency about important things to consider BEFORE attending a timeshare presentation in Mexico.
SEE POST #262 IN THIS THREAD FOR UPDATED INFORMATION
The best protection of your rights and responsibilities on any contract is to take your time to completely read and fully understand all the provisions of the agreement. Do not rely on what a salesman tells you because only what is written in the contract will be enforceable. Don't be rushed or pressured to sign something you don't understand. If you feel you are being rushed or pressured to sign, that's a big clue to stop and walk away.
Added 4-24-15: Watch this tv report about a presentation in Puerto Vallarta:
http://sacramento.cbslocal.com/video/11423455-call-kurtis-investigates-mexican-timeshare-nightmare/
TUG owner Brian Rogers is in this report, too.