Unfortunately for retailers, business is not like it used to be, and there is so much more competition so they need to have sales much of the time to survive.
Yes, having a Sale sign in the window or outside the shop influence me to at least go in.
I now generally only buy clothes in a sale, so I do not think there are too many from a shopper's point of view. However I often walk into a sale, and end up buying item or items that are not in the sale, so I guess the Sale signs are doing their work!
Sales are everywhere nowadays. This does not mean they are always real deals. It's just a marketing strategy in many cases.
However, I a sales sign does influence my decision to get inside and check the deal out. Clothes, for instance, I buy only when there are sales.
The sale signs look awful to me because they are usually red and imposing, but they do have an impact on my shopping too. If there is a brand on sale and a similar brand not on sale, I will go for the one on sale. It's hard to avoid.