Yes. You can just use a sheet metal screw and then pull it out with pliers. The idle mixture screw is likely the most important part of a re-jet.

 

I'm confused as to why Harley would put a plug that has to be drilled out over and adjustment screw

 

It is a tamper resistant device required by the EPA at time of manufacture to maintain lean emission standards. It was also done to carburetor equipped automotive vehicles.