Your pic is decent enough, looks well exposed, ok composition (think I'd have preferred a portrait orientation) not bad use of dof but I think this could be a really good shot if you managed to capture say someone littering as these guys were changing the bins. It would capture the frustration of this kind of job as opposed to two guys doing what they were hired to do.
Jackiex, I know what you mean about being nervous. I know I've missed a lot of shots because I was afraid of the person figuring out and getting mad that I was taking his/her picture. A lot of my early attempts at street photography were from the back. That actually helped because I was able to practice capturing a 'moment' without as much fear of discovery. After a while, you'll get braver. It helps a lot to make sure your camera's settings are ready to go and that can help you get the camera up to your face, click the shutter and get the shot much more quickly - often quickly enough that most people won't even realize you've just taken a picture of them. The more you fiddle, the less likely you'll get your shot. You have to also be prepared for many shots not coming out quite the way you'd hoped, but these all become worth it when you finally get the one you've been waiting for!
It helps me to think about worst case scenarios: someone gets a little pissy with me? I can handle that. Will someone potentially get violent if they are pissed at me? I don't want to deal with that so I don't take the shot and let it be 'the one that got away.' So far, I've found that most people don't care, don't notice, or don't do anything more than maybe give me a dirty look.
I hear you on being nervous and a quick shot trying not to be seen. I get that feeling too. I like the contrast of the workers light tops and the dark can and the DOF with the cars in the background. I would crop out the half person on the left.
Best would be if they had a real shocked expression on their faces as if "What is that!!!" when they opened the bin Oh the possibilities.