hmm... I don't really know what the weather is like down by you this time of year, but if you can (and if you have one) I would go for a classy but not too stuffy cocktail dress... something about knee-length, maybe one of those trendy retro-y dresses with the stiffer flared skirt, or even just a shift in a fun colour or pattern.

(Can you tell I love these kinds of events? I miss college!)