At Universal Orlando Resort yes, but at Universal Studios Hollywood early entry is for anyone who buys their tickets online.
As for the OP question, I would call the park and ask.
Also, do you have your tickets in hand? Are they a computer printout with a barcode or a hard theme park ticket (credit card size ticket)? If your ticket is a computer print out, chances are you will be able to gain early entry.
All the reports I've heard of people being denied entry are those whom buy their ticket at the gate or have a hard theme park ticket/processed annual pass.