Running tights...eh, his choice. Wouldn't really care.
Bike shorts: Cycling yep. I'd take it as a sign he's more serious about it. I frequently ride in bike shorts. One guy who frequently wears bike shorts beat cancer. And the French/the rest of the world 7 times in a row. Might have heard of him.
Running in bike shorts...I'd wonder why he needs padding on his butt and how much that's chafing...
Btw just noticed the question is for girls part. But I already typed this. So I'm gonna hit submit anyhow. Yolo.