I'm pretty thin and I don't have any muscle. I have a nice flat stomach, but my arms and legs aren't toned at all, they're just skinny. I'm not sickly skinny, but I'd definitely say I'm thinner than the average person. I have pretty good sized boobs, but my butt isn't anything to look twice at. Would it be weird if I went showing that much skin if I'm not toned? What would guys think?
There is no protocol that says you have to have a perfect body to wear clothes that show it off. :) Besides, people really only seem to get butthurt about seeing others who are very overweight showing some skin. I doubt you'll get any negative feedback if that's what you're afraid of.
Screw anyone that says you shouldn't. I'm not a size 2 and I still wear half shirt's and shorts. Besides you're going to the gym making a step in the right direction anyone that hates on you for that is just plain stupid.