UPDATE: Looks like the report from Mexico was hokum. Here's the latest from Yahoo! sports:
UFC heavyweight champion Cain Velasquez had one MRI on his left shoulder and is going to get another in order to determine if he needs surgery, his manager, Bob Cook told Yahoo Sports.
A Spanish-language web site reported Wednesday that Velasquez would defend his belt in the main event of UFC 172 in Mexico City on either April 19 or April 26 against Fabricio Werdum. UFC president Dana White told Yahoo Wednesday that is not true and that Velasquez's injury will delay any foray into Mexico.
From the report (originally in Spanish and mangled via Google Translate):
It's a matter of days for the UFC officially announced the first event in Mexico. The Arena Mexico City will host the Billboard 172 company, a pay per view for America that will be headlined by Cain Velasquez and challenger for the heavyweight belt, the Brazilian Fabricio Werdum.
The date, the weekend of the 19th or April 26th 2014 is perfect for the Mexican American, because even though the medical suspension was discarded six months after his last defense, if you have half a year to make full preparation. On Tuesday afternoon, the president of the promoter Dana White confirmed that the announcement will take place on Mexican soil as they become ready. That moment could come in the coming weeks as the company's promotional activity intensifies.
Werdum lost to Junior dos Santos at UFC 90 and then went to Strikeforce where he became the man to end Fedor Emelianenko's win streak, going 3-1 in the company with the lone loss being an uninspired bout with Alistair Overeem.
A late April date will mean that Werdum will spend almost a full year outside the cage.
One interesting wrinkle here could be using Cain to try and capture the Mexican audience. There is a longstanding rivalry in boxing (undisputedly the fight sport in Mexico) between Mexican and Mexican-American boxers. It's more of an on and off thing but it has been around for a long time, bubbling up from time to time. It's likely to not be a huge issue as Chris Arreola is Mexican-American and was received very well when he fought in Mexico in 2011.
That Cain isn't fighting against a Mexican opponent will likely mean that nothing comes of the rivalry, and I'm sure the UFC has plenty of market research to know how he has been received to this point. It's just an interesting little wrinkle that will be interesting to follow in terms of exactly how well he'll be embraced.