Yes definitely you need to come over and check out the Bay for a day/night or couple days!!
I can say that the people watching would be great from one of the benches in front of Frosty's, Roundhouse, or Mr. Ed's as that is where a lot of the action is at night!
As for the dress attire. There is literally a very wide range of dress at the bars: shorts and t-shirts, jeans and collard shirts, dresses, skirts, I have even seen some girls wear a bikini top to the bar with a pair of jean shorts... Whatever you decide to wear you will fit right in unless you wear a suit LOL!!
There are about 15 bars within a 3 block radius in downtown which is where 90% of the action is. There are a few bars in other parts of the island, but for your first trip I would stick to the downtown scene and you will not be disappointed