There's a small (not entirely well marked) on-ramp to I-4 (West Only) from "Adventure Way" on or very close to Universal property. (I couldn't tell you how to get to it from the RPR, I'm usually coming from outside of Universal, rather than inside of Universal)
(Edit to add: Watch your speed on this street ... there's a blind curve that's a 35 mph limit, a lot of people go faster than that. I've seen Orlando Police Dept running a speed trap there on more than one occasion)