Depends on your field of interest and your goals...
- if it is to get an LOR, as others have noted, its too late
- if its to get an interview, it might be too late, although many programs give "courtesy" interviews to anyone who has rotated there
- if its to make a good impression or see what a program is like, its probably fine - ROL aren't due until mid February and most residency committees won't formalize their list until shortly before then