on Orlando Hotels and Attractions board either by doing a search or making a post if you haven't already for this particular Marriott. But, as far as I know whether or not a specific hotel's bus shuttles makes a stop to another hotel is going to really differ and vary greatly according to that particular property.
I have heard some guests mentioning their shuttle buses making an additional stop whereas others report that none were made. For instance, we used the HoJo Maingate West shuttle bus in 2000 on one day while on vacation to visit Epcot before picking up our rental car and the driver didn't make any other pick-ups or drop offs; our hotel guests (not all of them) were the only passengers aboard. Also, I would definitely suggest making direct contact with the hotel to inquire about the exact times and days of operation during your vacation for traveling to each park. Hope this helps some.