The closest is Stage 54 at USF. Stage 54 has behind the scenes displays on The Mummy Returns. Stage 54 changes every few months, but it was still up when I last checked in August.
This one i can answer: The mummy is in the Horror make-up show building across from Mel's Diner and La Bamba. There are props inside and some explainations. there is also outside the bus they rode when the whatever they were, were chasing them. The things are on the bus, or all over the bus to be more exact. After the first room is the make-up show and it does hilite some of the mummy items