You'll be surprised. New England and the East Coast in general has huge Spanish speaking populations. NYC of course has a huge Spanish speaking population and many of these people moved upstate, to New England, and down the eastern seaboard. Certain places like New Haven have 30% Spanish speaking and up to 60% of patients are Spanish speaking (yes I shadowed there). Even in Maryland/DMV I see a lot of Spanish. My physician that I shadow say she loses patients sometimes because she cannot effectively communicate or they cannot get a translator and she wishes she took Spanish in undergrad, also even people that speak some English may not be able to communicate stuff to the doctor. For example, asking someone with very limited English wear does it hurt, your abdomen, is it tense etc. many be too complicated. Honestly, I think Spanish is an absolute requirement now days. Seriously.
In terms of medical admissions, it won't "hurt you" because you can learn it in medical school "medical Spanish etc." I think it will hurt you career as a clinician AFTER medical school if you dont have a grasp going into residency.