When we were there last week, we checked the walk-up list for two places, both were 55 minute waits to join the list.
We were in HS.
Hope that helps a little.
The way I understand it, if you're not nearby, you'll get a message that says the waitlist is full, though I've found that checking from another state does show some wait times at places like GF cafe. I've also heard that the waitlists tend to fill quickly, so it's advised to join ASAP at the start of either the lunch or dinner periods. My uneducated and unverified theory is that places in the parks or popular resort TS restaurants won't show in your MDE unless you're within at least WDW property, if not the resort/park itself.