Hi Jasonicus, Here is your answer, courtesy of the inimitable Wikipedia:
"The location of the Super Bowl is chosen by the NFL well in advance, usually three to five years before the game. Cities place bids to host a Super Bowl and are evaluated in terms of stadium renovation and their ability to host. The NFL owners then meet to make a selection on the site."
Here are a couple of more wonderful facts about the superbowl which you probably never wanted to know:
Superbowl Sunday has the second-highest food consumption all year, just after Thanksgiving.
Superbowl games are always designated with Roman numerals, and last year 2010 was XLIV, the most watched TV show in all history, booting out the last episode of MASH that held the honor for so long.
The NFL does not award Super Bowl Games to stadiums that are located in climates less than 50 degrees unless the field is completely covered by a fixed or retractable roof. The location is chosen by the NFL usually three to five years in advance. Cities place bids to host the Super Bowl. The stadium renovation and their ability to host is taken into consideration. Then, the NFL owners meet to make the decision on where the location will be.