People have no legal expectation of privacy when they are in public or a place visible from the public space without the aid of telescopic equipment. Therefore, in these areas, their photo can be taken without their consent. However, you can not make money off someone's likeness without their consent. Since they are being used for promotional purposes, you may want to have those particular people execute consents out of an abundance of caution. The hospital should have a staff attorney and that person would be able to better advise since he/she would know better how these will be used presumably.
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