If public speaking isn't your top strength, try using visual aids such as a colorful poster board or flip chart with key points or handouts to help bolster your speaking presentation.
Since this is a multicultural admissions recruitment role, you might want to try for topics like why going to college is cool. You could talk about campus life and how it makes college years memorable: student clubs, athletics, living in the dorms etc. Why college is beneficial: increased job opportunities, better pay, career center help. Why college is possible for them: financial aid opportunities, on-campus tutoring, academic advisement, work study program etc.
I find it odd that your interviewer would invite you to come in and only give you one day to prepare a presentation. That's kinda harsh!
Just do your best and remember to smile a lot! Best of success to you!
.....Kelly