For Girls Only, unless you're gay, then I guess it's OKAY!

I'm gay and 18, and I must say that you do sound rather attractive.

However, I hope that you don't mind being shirtless in public — like, you're walking down the road on a hot day, and you feel hot so you just take your shirt off. Or you're doing some sort of sport in the park with friends on a hot day, and you feel hot and sweaty, so without any hesitation at all, you just pull your shirt off, totally unconcerned that your muscular chest would be fully exposed to your friends and anyone else present. Or you'd even generally be shirtless beforehand in such circumstances, in order to prevent yourself from getting into an undesirable hot and sweaty situation. Then even better, hopefully you'd remain barechested afterwards, not feeling the need to put your shirt back on assuming it was still hot enough.

Seriously though, I really love seeing fit guys my own age shirtless outside in public, especially if they're doing some sort of physical activity — I find it really attractive, for some reason, so maybe straight girls do as well. Hey, if you manage to get a girl to go out with you, why not conveniently find an excuse to casually and naturally bare your chest in front of her? — confidently pulling it off as you walk/sit-down outside, making some 'ooh, it's so hot' noises in the process. ;)

(Sorry for fantasising at your expense!)