Hi Annette,
You can leisurely walk from the
Bay Lake Tower to the main gate at the Magic Kingdom in 15 minutes or less. From there, the stroll down Main Street, USA towards
Cinderella's Royal Table is brief. The amount of time it takes depends on how many stops you make along the way (it can be tempting to browse the shops). I would give yourself 30 minutes from your room to the Hostess stand. Of course, if you would prefer to take the monorail instead of walking, you could do that as well. Be sure to factor in the need to arrive 15 minutes prior to your scheduled seating time.
The 90 minute estimate that you were given would be worst case scenario from some places at Disney
to others that are a long way away from each other. Bay Lake Towers to Cinderella's Royal Table is not one of these cases. An example might be getting from
dinner at the Animal Kingdom Lodge back to a room at Port Orleans French
Quarter. This can take a bit of time sometimes. This is because the buses
don't run from Resort to Resort. So, you'd need to head to a Park or
Downtown Disney first, then transfer buses. If you've just missed a bus,
it can take up to 20 minutes for a new one to come, which is why you
should always plan on extra travel time.
Hope this helps and have a wonderful vacation,
Kaylene