Bus transportation inside WDW

[DISFANSHAN]

I was sure that only WDW guests were allowed to use the bus transportation to/from parks and resorts. But then I saw a thread that stated as long as you pay for a park pass, you are entitled to use all of Disney's transportation...monorail, ferries, and buses. Not for nothing, but this will be the first time we are staying on site and want to take full advantage of the busses, but not if they are crowded w/off site guests. (no offense, but in the 8 or 9 times we have been to WDW, we have NEVER used the busses).
If only resort guests can use them, do they have to show resort ID upon boarding?

 

[KilleriMac17]

If only resort guests can use them, do they have to show resort ID upon boarding?

it is one of the perks of staying on site, BUT,I have never seen them check, but I have heard it busy times they will sometimes do random checks, or will check each person trying to get on the monorail. but I haven't actually seen it, only read about it here.

 

[Chip 'n Dale Express]

The only buses that are crowded with day guests are the park to park buses. I wouldn't worry about it at all.