If you take 8 to the 85 coming from Yuma you'll never get to what I call the split (8 & 10 in Eloy). If you go north on 85 at Gila Bend it takes you into Buckeye on 10, and then you have to cross all of Phoenix on 10 going east with heavy truck traffic and there is a lot of construction on 60 coming into Mesa.
There are two other ways to go.
About 40 miles or so past Gila Bend on 8 there is a road that goes off to your left that crosses the Gila indian reservation and takes you straight into Chandler, Gilbert and Mesa from the south. I think its 347 or something like that, but it might be marked as 84 as there is a Y north of the exit. Beats the superslab.
The other way is to follow what eventually turns into 87 out of Casa Grande, but it's longer and easy to get lost on. Bunch of little roads (187, 287, 387) that do strange stuff. Good day ride though.
Up to you, see if you can find 347 on a map, if you don't run 85 mph on 10 you will get run over. Good thing is here you can run the HOV lanes with a bike if you have to take the slab.