You have to keep a couple things in mind. First off, there is advertising which you expect an immediate return on, then there is marketing or branding which takes time to bear fruit. Sometimes they are one in the same. With advertising like fliers, you hope to see returns immediately or within a short period of time. With branding and marketing, the idea is to get your name and your branding (colors, logos, tag line anything that separates you from the rest) recognized and remembered. You basically want your business to become a household name. This takes time and it takes more than just one form of marketing. For instance, if you have a bill board, yard signs, TV commercial, etc that is consistently seen, then eventually people will remember your business and hopefully remember you when they need something done. Whereas with advertising you are hoping they need something done right then and there or that they hang on to your advertising. In many cases, the right type of marketing will make your business seem more established and give you creditably. Its the type of thing that if done right, makes people go "oh yeah, I have heard (or I know them), I heard they were good (or they are good)" and they will say these things even if they have never used your services.
Point is this, do not expect to get any business from the yard signs, but hopefully if people start seeing them, your business name, logos and colors consistently around town or online, then they will remember you in the future. You will appear to them to be more established in many cases. These types of advertising are the types you can't really track. If you were to ask someone how they found out about you, they probably would not say a yard sign.
