.. and for those TVs that don't have the "phone cord" (or ignore input settings even after it's been disconnected) LG (the maker of the TVs in 99% of the Marriotts I've stayed in) sells an "installer remote" that typically runs ~$20 and has buttons (Google for details) that will give you access to any of their TVs.

IMO, Marriott has gotten better about not locking out inputs lately, and ironically enough, just like so many other things in the chain, the lower-end hotels tend to lock inputs far less than the FS ones do.