Just read this quote from Universal Orlando RE Opening times from July 8th and Early entry until early August:
OPENING TIMES FOR JULY 8
The Grand Opening will take place at The Wizarding World of Harry Potter Diagon Alley in Universal Studios Florida between 8:00 am and 8:30 am, with all other attractions opening at 9 am. Universals Islands of Adventure will be open at 9 am.
However, we will be ready to accommodate guests as early as 5 am on Tuesday, July 8 only. That is when the parking plaza will open and transportation from our on-site hotels will begin.
For all other days, follow the posted times listed on our website.
EARLY PARK ADMISSION
Early Park Admission (beginning one hour before the theme parks open) is available for on-site hotel guests, vacation package guests, Virgin Holidays guests, and guests who purchase a 7-Day length-of-stay ticket.
On July 8, these guests may enjoy Early Park Admission to Islands of Adventure beginning at 8 am, where they can experience The Wizarding World of Harry Potter Hogsmeade.
Starting July 9, both parks will be opening at 8 am through early August. Guests with Early Park Admission can begin enjoying Universal Studios and Islands of Adventure beginning at 7 am. We encourage you to enter through Universal Studios on one day of your trip and Islands of Adventure on another to experience all of The Wizarding World of Harry Potter.
HOGWARTS EXPRESS
The Hogwarts Express is scheduled to begin operation at 9 am on July 8.
On July 8, to ride the Hogwarts Express from Kings Cross Station in Universal Studios to Hogsmeade Station in Islands of Adventure, youll be asked to wait in the Grand Opening queue line in Universal Studios.
On July 8, if you ride the Hogwarts Express from Hogsmeade Station in Islands of Adventure to Kings Cross Station in Universal Studios, you will then be asked to wait in the Grand Opening line to enter Diagon Alley or to ride the train to back to Hogsmeade.
This was quoted on Snitch Seeker and I haven't been able to find that exact announcement on Universal's site - still it sounds fairly reliable