Hotel Plaza resorts use Fleetwood Limousine (sometimes dba Bethany Limousine). They run every half hour all day long.
I don't mean to worry you, however I have never heard anything good about the service to Hotel Plaza... I recently knew an aquaintance stay at one of the Hotel Plaza resorts, and use the bus service. Horrible service at best. I told him to write to the hotel, and have them address the issue with Fleetwood/Bethany. Hopefully it might provide some results.
As for firsthand info, I can tell you those drivers have lead feet. I'll be doing the speed limit, and they'll zoom past me like I'm standing still. Condition of thier busses is mediocre... all banged up, filthy... albeit not nearly as bad as some other companies.