Dena---thank you for your kind wordsS So sorry I didn't respond sooner; I haven't looked at this entry lately, and evidently there's no notification that I have a message about it!
I used mortar all the way. I used Speed-Set on the inset decorative tiles, and also on the vertical tiles on the step riser I just completed. It's a lot stickier and easier to work with than regular mortar. But for the big tiles, I used the (much cheaper) regular mortar.
When I'm working alone, I mix mortar and grout in a big stainless steel bowl, not in my concrete mixer. Setting the tiles takes me too long by myself and if I made a big batch it would just go to waste and be a mess to clean up. When I did parts of the walkway, I had a couple of friends helping and we did bigger sections. And I had a contractor do part of the inside courtyard floor last summer----otherwise it would have taken me a WHOLE lot longer!
I started this project in 2004, and just finished the last section of the original planned design----but I wasn't exactly working straight through! I have one added project to complete, and then the walkway and courtyard will be done. But I'm still making the tiles for the latest project, which is a curved raised hearth for our cast-iron chiminea.