Original Poster says:
"At the end of the movie, Alice broadcasts a new message from Arcadia, which is supposedly off the California coast in the Los Angeles area. She gives the location of the ship as "118.30 degrees west, 34.05 degrees north." these coordinates would place them Just north of Sucheng, mainland China!"
You're nearly right - the location you describe is 118.30 degrees EAST of zero longitude (Greenwich UK).
118.30 degrees WEST (can also be written as -118.30) is, in fact, Los Angeles. However, it's still a slip-up, because it's not in the ocean; the coordinates actually point to South Normandie Avenue, near Westlake, roughly 20 kilometres east of the coastline.
The first Arcadia location, about 20 minutes into the movie (where Alice is flying to in a plane) was correct: Juneau, Alaska, and close to a shipping cove, which makes perfect sense.
You'd think they could spend 5 minutes with a mapping application and get the other location correct too. Maybe it's the home address of someone on the production staff or something...?