In short, the answer is No. Your softener will perform best if it's programmed based on the true hardness and iron levels in your water supply.
Why Not?
When setting your hardness number, you're telling the softener the amount of hardness minerals that's in your raw city/well water. To calculate this number, follow our How to Program Your Hardness Level article. This is important because your unit uses the hardness setting to determine how often it needs to recharge. If you set the hardness higher than it needs to be, your unit will still give you the same degree of softness (0-3 gpg), but it'll use more salt and water because it'll perform more recharges. This isn't ideal. Setting the hardness number higher than necessary reduces the efficiency of your softener.