Hello Colleen!
As you are probably well aware,
Walt Disney World has
multiple protocols in place to help keep Guests and Cast Members safe and healthy. The state Florida Division of Emergency Management did host the Maingate Testing site, but closed it in May.
Since you do not have a car, your best bet is probably the Orlando International Airport Covid-19 Testing Clinic on your way home. The clinic is open until 5:00 pm during the week and 7:30 on Saturday and Sunday, though the PCR test is "subject to availability". Appointments may be booked online.
Another option is to take a ride share or taxi to a local pharmacy or urgent care offering rapid covid results. Advent Health, CVS, and Walgreens provide this service at many of their nearby facilities.
Wishing you a wonderful adventure flying with Peter Pan, plummeting down mountains, and spinning in tea cups.
Elisabeth