It has been announced that Rafa will play an exhibition match on March 21 in Bogota, Columbia.  His opponent will be current World # 3 Novak Djokovic.

Google translation.

This was confirmed by the signing Imlah, organizer of the exhibition game. Not yet set the scene.

Nadal's presence at that time was to take advantage of free days that remain between tournaments in Indian Wells and Miami.

The meeting will take place at the Plaza de Toros La Santamaría, setting this year was the confrontation between Colombia and the United States, for promotion to World Group Davis Cup.

Source 

UPDATE:
Another article from ELPAIS.com

And so the firm Imlas confirmed that it will organize the exhibition match, although it has not chosen a location.

"Hello, Colombian friends, I'm Rafa Nadal. We'll see each other on March 21 in Bogota in a match where I'm going to play against Novak Djokovic. I'm very happy to go to Colombia for the first time, and I hope to see you all there. A big hug," stated Nadal during the confirmation of the news done by the company Imla de Colombia, organizer of the meeting.

The president of the company, Manuel Mate, provided in a press conference in Bogota that the encounter will be played in this city in a location yet to be determined. He commented also that the objective of bringing the Spanish tennis player was nailed down at the US Open this year, when the parties agreed on the terms (very loose translation).

"The project began in March, searching to land Rafael Nadal to play a match during the 2011 calendar. Then in September, at the US Open, we met with his agent, and we began to search for a date that had to be during his playing months and was approved by the ATP and which wasn't inconvenient," stated Mate.

"Thus March 21 is a perfect day, with both players coming straight from Indian Wells which ends on the 20th, and the United States and Columbia are not far apart," he said. Regarding contact with the Serb Djokovic, Mate commented that he thought of him as one of the best in the world.

"It seemed to us that we should look for a very good opponent, and we thought of Djokovic because Rafa's PR guy also manages him," he stated.

The commercial manager of Imla, Alvaro Falla, commented that he also thought of the Swiss Roger Federer, number two in the world. "What could be better than Nadal in Colombia, well Nadal and Roger Federer, logically we tried that, but it wasn't possible," he said. "But just the same, this is great news for the country, just as the exhibition between the Americans Andre Agassi and Pete Sampras was, but this is doubly interesting," he assured.

The company reps commented also that they are thinking about other very good players to make a spectacular opening act before the Nadal-Djokovic match, but that hasn't been made concrete. In terms of demands, the players have made few.

"They are very simple players, they aren't rock stars, they're athletes. They only want a good hotel, good transportation, and good food, and we're going to work on arranging a private jet," he said.

Finally, Manuel Mate recognized the closeness of Nadal, who filmed a video with the Colombian singer Shakira, could influence his desire to come to Colombia.

"Speaking of the tabloids, Rafael Nadal's knowing Shakira is one of the factors for his coming. It's no coincidence that he'd made a video with her, and that's a real connection with this country," he affirmed.