>>>Do they allow purchases from the cage or table only?

It never hurts to ask but unless they have changed since I was last there, you may not purchase chips from the cage and the table chips are generally in "very well used" condition. You will really have to search to find decent ones.

The dealers are very chipper friendly and will help you (I had roullette dealers that went through every chip for me) and they will sell (oops I mean "lend") you all the chips you want.

Enjoy your trip.