No, no, no and no! We tried this one morning (our first morning). We were all ready to go and the MK bus was there but we didn't make it on because the que was full. My DMIL was back at her room eating her breakfast when we left her. We got on the EPCOT bus and transferred to the monorail and waited for that. Then it stopped at TTC and we had to switch monorails to get to MK. As we were getting off the monorail my MIL called my cell and said she was on main street and had been waiting for a few minutes. She finished her breakfast, brushed her teeth, went to one last potty break and then got on the bus and she still beat us there by about 5 minutes.
It seems like it would be faster when the EPCOT bus is waiting there, empty, taunting you, but it's not.