Without knowing your opinion of fun atmosphere I like Zin American Bistro. Tables are close and you can often meet interesting people dining next to you. Matchbox is fun - food is good probably not great. St James is very eclectic mix of food and atmosphere. Live music after dinner.
You should know that St. James is VERY pricey...expect to pay $30 for an entree. Las Casuelas is fun...live Mexican band and good food...maybe not too authentic, but tasty and better priced than most downtown. Should meet folks at the bar there or even at a table having dinner.