You're free to make a motion for a change of venue at your arraignment... Although pursuant to VC40502(b), a request to transfer would be to the county seat of the county in which the offense is alleged to have been committed. As such, and in light of the fact that "Los Angeles" (where Metropolitan is located) is the county seat for L A County (NOT Downey), I'm not too confident that your request to transfer to Downey qualifies as a proper request.
If driving the 15 or so miles between Downey and Los Angeles is that big an issue, then you still have the option of a Trial By Declaration.
Good luck!

