The observation deck you definitely can. It’s on the outside of the Contemporary and open to anyone. From BLT, just take the walkway connector and before you get to the door to the Contemporary you can turn right and the observation deck is right there. The monorail tracks are above you, see you can also see the monorails coming into the Contemporary as well.
I’ve never stayed at BLT, but from what O understand, as long as you are staying there you can get into TOTWL.