Andrew: the US Multihull Championship for the Hobie Alter Cup is an invitation-only closed event. The participants are (mostly) chosen from the different US Sailing areas over the country by winning their local "qualifier". Being in Florida, you're in Area D (South). In order to qualify to sail in the championship in 2010, you need to win the qualifier in Clearwater Florida. This is the event they're talking about.

Sailing in the qualifier is not unlike sailing in any other regatta (except that all boats start at once and are scored only on handicap), its just that the winner (and if your area has the largest participation, the second place team) gets to go the championship.