I like to think that your research mentors are truly there to help you and inevitably, to write you a strong letter of recommendation unless they say they don't know you well enough to provide that. I would try to have these conversations soon, in case someone on your list cannot provide you with a letter of recommendation.
I'm primarily interested in cellular and molecular neuroscience with a focus in neurodegenerative diseases, and I've found a few mentors at Baylor, UT: Houston, Texas A&M, University of Utah, University of Iowa, and Tulane with research interests that mesh really well with mine!