February is a bit late for summer internships in my experience–most students have probably already accepted one already for fear of not having one over the summer.
Maybe YC & YC companies can bring some order to this internship arms race by establishing clear application/decision timelines for YC companies? My sense is February is too late, but September-October applications for November decisions might work well.
As a former student and then recruiter for the SV company types, the Spring career fair was pretty good at filling up the intern roster. Definitely the fall is much much better for full-time & junior candidates.