I'll pick the blue one with a suit.

Flower one is too fancy, definitely not for any conference.  40% off on sale items @ Ann Taylor now, maybe you can find something there.  Just to give you some ideas, these two dresses I think they will work for your presentation.  Last time I got 60% deal on all sale items, maybe you can wait until July 4th weekend, maybe they have more discount. 
http://www.anntaylor.com/petite-cotton-sateen-v-neck-sheath-dress/341513?colorExplode=false&skuId=16303522&catid=cata000047&productPageType=saleProducts&defaultColor=9000 
http://www.anntaylor.com/petite-jeweled-neck-tweed-dress/341501?colorExplode=false&skuId=16492141&catid=cata000047&productPageType=saleProducts&defaultColor=1212