Lee, you seem to think all people have this inate ability of perfect pitch..lol I wish. "Play what you hear in your head", you say... You actually make me smile alot and I thank you for that but alot of people that ask these types of questions are not to a point where they can hear it and apply it without though, as for me when I solo I don't hear anything I just catch the rhythm and let my fingers start doin' their own thing. I have ran scales enough times that my fingers know what to do with out me thinking or hearing.
My advice to anyone just getting into soloing is cruse the internet and find licks and small voicing patterns you like the sound of and learn them. Note what key they are in so you know thier root and then you can apply them to any key. The hardest thing for most new soloists to do is give the scales voice rather than making it sound like your walking up and down a scale. Also throw in a few bends when your practicing scales, you will star learning what soounds good to you.
Theory is good to know, I learned theory long before I picked up a guitar while playing trumpet in Jr. High band but knowing why this or that does or does not sound right is good knowledge to have.