First off - Hello Tom from Delray Beach! I am Boca Jan - from Boca Raton. LOL
I use sandbox sand. It is clean and when damp holds the tunnel they will dig perfectly; and it is inexpensive. Have they given up food yet? Wandering around the bottom and giving up food for a day or two are signs that they are ready to lay.
Cover your container - I use a rubber bathroom sized trash can filled with damp sand to about 3" from the top. The sand should be damp enough to squeeze into a lump when you pick up a handful. My ladies have never had a problem with this size. Put a towel or something over the cage so they feel very safe and let them do their thing.
For incubation I use a clear shoebox with 2 holes punched in the top on either end. I put about 3" of vermiculite (purchased at Home D or lowes) and moisten it. When you pick up a handful of this the very most you can squeeze out would be a drop. I never made mine wet enough to get that drop out.
Make a little indentation with your finger and lay the egg in the indention, trying not to turn the egg from it's laying orientation. When done, label the box with date and which female laid the eggs and stow them away. Mine stay in a little used closet at 75 degrees which is my house temperature.
Please read the Kitty blog below. It is a pretty inclusive article on keeping chameleons. Kitty is a male veiled, but the care of an ambilobe is about the same. I have an ambilobe and it gets the same care as my veileds. Good luck neighbor!