Not sure about Evo camera app, but on a Samsung, you cant change the folder where photos are saved from the camera app, not that I know of (not unless you root it I guess). If they're settings menu is the same, you cant as well. However I think you can check it
I also have DropBox, but for what you want to accomplish, what I do is that I use SugarSync for that. It works like DropBox, where it creates a folder (In this case "Magic Briefcase" in My Documents) where anything you put in gets sync. In addition to this, it allows you to sync a specified folder from your phone to this folder (you can choose multiple folders), in your case the folder where the pictures get placed by the camera app. This folder would appear in your PC inside My Documents>Magic Briefcase>Mobile Folders. If you cant find any other way, you may want to check SugarSync out.