Mine as well. I am not in AZ but I have hot summers and old growth Bermuda grass (43 year old property) here.
The only thing I know of that will slow it down without using poisons is shading/covering it with something.
This lasagna bed was new last year. I bordered it as shown, border slightly pushed down in the ground so that the Bermuda tends to want to grow up the side of the border more so than under it ... and is easier to pull/cut. I had the ground around it covered with bunched up landscape cloth to shade it (removed it for something else later) and you can see that the Bermuda is just now starting to invade that outer area in this shot on Sept. 1.
Bermuda does go dormant in the winter here so we are fortunate in that way.
