No, it looks cheap and trashy. Ever seen a model or a celebrity on the red carpet with a bra showing? Nope - it's just not a good look. If a top or dress cannot hide a bra, that is because it was designed to be worn without a bra. And that's an extremely cute, confident and attractive look. Be brave - I understand braless can be scary but it's a great look in the right top/dress, be confident in your body and be proud - bras are not mandatory, they're just habit! :)
I've never thought bra straps were a big deal. I figure that since I'm a girl, people won't be too shocked to find out that I'm wearing a bra and I've never understood why some girls find it so embarrassing. Most of the time they just look like tank top straps anyway.