Notifying your creditors about your decision to file bankruptcy is a personal option. It may depend on how comfortable you are talking about it as well as how soon you plan to file. Many people who file often don't say anything to their creditors, instead they wait till the courts notify them in order to stop collections efforts.
There's no way of knowing how creditors will react to your intention of filing. Creditors may offer to settle the debt with you or even create a payment schedule. Just keep in mind if they decide to forgive a portion of the debt you may be required to report that information on your tax return. Upon learning about your intent to file they may forward your account information to their legal representative, something they usually do as soon as they think legal proceedings are taking place.
If you plan on telling creditors about filing, do so after you have chosen the bankruptcy attorney you plan on filing with so you can forward your bankruptcy attorney contact information immediately. Forwarding the contact information of your attorney often stops creditors from continuing to contact you immediately rather than avoiding their calls until they are legally noticed by the courts.