So where does Hollywood party-hopper Paris Hilton think they should go to unwind during their stay?
"[They should go to] the Beverly Hills Hotel Polo Lounge because it's private," the heiress tells us. "And they won't be bothered with paparazzi outside like you would at the Ivy or something."
Hilton's aunt, Real Housewives of Beverly Hills star Kyle Richards, has somewhere a little more public in mind for the couple. "They should go to a concert at The Hollywood Bowl," Richards says. "Pack a picnic dinner and bottle of wine!"
One self-described royals fanatic royals-obsessed celeb has a selfish motive for her suggestion. "I want them to go to SoHo House so that I can see them there," Jamie King says. "I would go to any and every royal event. I'm obsessed with them. They are amazing, they're in love and they give us hope."
Brit actress Jane Seymour tells us, "The Duke and Duchess have to make time for Universal Studios. A great day, great fun and great rides and attractions. They can't visit L.A. without making time for some theme park fun!"
Or a bite to eat in a section of town just east of Hollywood.
"They should go to Blair's in Silverlake for dinner," Horrible Bosses actor P.J. Byrne says. "It's the best restaurant in Silverlake, maybe the best restaurant in Los Angeles."
Gretchen Rossi of The Real Housewives of Orange County suggests a visit to the suburbs.
"Visit Huntington Gardens in Pasadena," she says. "It is a series of glorious floral gardens that are breathtaking. There's great architecture, artwork and they can sit and have tea in the Rose Garden."
"They should go to the Griffith Park Observatory," says Nickelodeon teen queen Victoria Justice. "You can look through all the telescopes and see all the planets and different moons... They have this auditorium where you lay down flat back in these seats and you look at the stars and it tells you all the information about the constellations. It's amazing."
And so is a trendy restaurant in Little Tokyo.
"Go eat at the Shabu Shabu House there," says Grey's Anatomy cutie Chyler Leigh. "I am promoting Shabu because it's one of my favorite meals on the planet."
Note to William and Kate: Shabu Shabu doesn't take reservations so be prepared to stand in line for a table.
OK, maybe not, but just thinking about that made us laugh.
—Additional reporting by Meagan Medick
ALSO! We'll be livestreaming William and Kate's arrival at LAX, so check back at E! Online tomorrow at 3:30 p.m. PT for the big royal welcome.