#1
What sort of scales or modes would I be better off learning to improv in the style of John Mayer gonna find another you live.
#2
Just checked it - it's a bit trickier than a straight blues, you need to follow the changes. That being said - these are a good start :

Major scale 
Major Pentatonic
Blues scale ( minor pentatonic with a flat 5)
Dorian 
Mixolydian 

Primarily it's major , but you can swap in some minor lines where it works. 

Treat each chord as it's own world - meaning be aware at all times of what chord is playing and remember what works over each. 
#3
Thanks for that mate. That's given me plenty to crack on with. Gonna be a busy few months. Just got myself a squire Tele and a little vox amp. Time to make her cry!!!
#4
John's playing isn't anything complicated.  I think reverb66 pretty much nailed the entire corpus of Mayer's scale choices on every record.  Learn those, transcribe and you'll see who/when he changes modes and scales to agree with the harmonic progressions.

Cheers,
Bryan

bryanclarkmusic.com
#5
I`d also suggest you listen to some BB King - he plays a lot of major blues and John is largely inspired by him when playing over those types of changes. Bb really is the authority on that type of playing, the major bends etc.
#6
Or Robben Ford, Larry Carlton, Albert Collins.  all of whom also love to use the Maj 6 pentatonic over blues progressions.

Cheers!