If I am cycling to an event such as the one you went to, I would be dressed exactly as you.
That said, I love the "flirty, strappy" dresses you described others wearing. I love dressing up. I also love cycling clothes. I see nothing wrong with what you were wearing, especially to a cycling themed exhibit. However, I do not ride to most "events" and I would not look as "nice" as you do, as I get sweaty, helmet head, etc. even from short rides.
One time, though we were in Martha's Vineyard and rode to Edgartown for lunch. We went to a "nicer" restaurant (it's a kind of snobby place) and the people could not get over our attire; mostly my husband's, though.