I think that "I want to show you my socks/youtube video" = "I want to spend time with you now and need and need an excuse to get you to come inside".
I also think that you may be an introvert and enjoy your time in the garden alone and they may be extroverts and want to rescue from being alone. :-)
Also, why are these guests staying at your house?
Is it to visit you?
Is it for a temporary place to stay?
If it is the former, then they may feel that you aren't spending time with you.
If it is the latter, they still may feel that they aren't spending time with you or don't know what to do with themselves..or feel weird that they are at your house but are not with you.
Also clarify what your expectations are...do you expect them to entertain themselves? Do you expect that you can go about your normal business and they can do theirs?
So my suggestion is that you try to figure out the motivation for the "yellers"....
So if you suspect it is that they don't know when they will get to hang with you next, you could pre-empt them and say "Guest, I am going out to the garden for about an hour. After that we can <whatever>".
And if someone yells from teh porch just say, "Come out to the garden. I can't hear you. OH, here are some shears, could you trim those bushes?"
Either you have a new helper or you have trained them not to bother you in the garden.