I am in the process of returning to IP/patent work (getting USPTO reg etc) and want to avoid that issue in the future.
The "issue" being working on matters that are "EE" but are outside of your work experience ("electrical power, controls, protection, motors, wired and wireless communications and networking").
Is it easy to find firms that only or nearly exclusively have clients dealing in technologies with which you are comfortable?
Well, that depends on how narrow your comfort zone is, right?
I'm a CS, not a EE, but I work at a firm that does lots of "EE work" -- and your work experience seems reasonably broad to me. You didn't list semiconductors, analog design or processor design as areas of expertise, but other than that you seem to have listed the big ones. Based on this, I'd say you have a wide range of firms to choose from.
Is it a negative to emphasize your tehcnological interests & experience to firms?
It's a *positive* to emphasize those two things. And as I said above, I consider your range to be broad, not narrow.
That said, it is a *negative* to say "I don't want to work outside of these areas". I'll go further than that and say that working in a wide range of technologies is one path to success in patent pros. Not the only path -- but a path.
My previous experience (1-2 years) was with a biglaw firm where IP was only one of a myriad of practice areas and many non-tech JDs & commercial litigators were among the "IP" group. I am pretty certain I would only want to work with a boutique IP/patent firm.
Makes sense to me. I decided that too, and didn't even have working at a GP as a comparison, like you did. I have no regrets about my decision.