Interesting topic but something I can relate to as I had a gf who is a "tomboy" who is not a lesbian, who is not rough or swears a lot, who smokes while I don't lol, always wear jeans, a bit rocker chick style, would rather die than wear a dress or heels. I think on a scale of 1-10, 1 being very feminine and 10 being the very tomboy, i'd give her a 6.5. Ok now that thats clear, I was perfectly fine with her being a bit of a tomboy.

Now to your questions.

How do you all react when you see tomboys? What do you look in us? What is particularly going on in your mind?
Honestly, I don't really notice but when i cannot decide whether the person i'm looking at is a guy or a tomboy i... look at the chest area. heh sorry but thats the easiest way to determine.

Particularly if you are straight male/female, how do you find or will react noticing tomboys?
I think if you're a tomboy but interested in a straight male, I think you shouldn't need to hide your tomboy-ness but rather tone it down a couple of notches depending on how high you scale on the 1-10 scale i used above. If you're 7.5-10 then you will attract lesbian girls. 5-7 tomboys, i think some guys fine them attractive.

For girls who are attracted to girls, would you prefer being together with tomboys?
Not for me to answer.