It will get noticed. I have no idea if the turn it down for its republican originations was internet sarcasm or not, but dear god, no don't turn it down.
More importantly the work you did to get the award(sky high GPA, great research work) will get noticed, as will the work you do after it with your $7500. Somebody capable of winning the Goldwater Scholarship is exactly the type of person who has the qualifications that can generate strong interest from MD/PhD programs(of course with the MCAT the big variable), that's the most important thing of all.
And yes for anybody who doesn't know about it, it is as prestigious a scientific undergraduate award as you'll find out there. Schools themselves are only allowed to nominate 4 candidates and often times have over 100 candidates to pick from for those 4 spots. And keep in mind, the average GPA of a Goldwater scholar is over a 3.9; if you don't have something close to that your wasting your time even applying.