Does pin A15 on a Z80 tell if the CPU is addressing ROM or RAM?
Look at the schematic on the following page.  A15 is connected to the chip selects of the ROM and RAM to make that happen.  It's not a function of the Z-80 per se -- it's a function of how the external memory is laid out.

Good choice -- the Z80 was the second microprocessor I ever worked with (in a TRS-80), and the first one I was paid to develop software on (at 13 -- you gotta love family businesses).