[LisaS]

not a physiologist, biochemist or dietician - just a bio major who sometimes stays at a Holiday Inn express.

You probably know this but I'll reveiw.
Insulin doesn't actually directly accomplish the uptake of glucose by the cell.
Uptake is actually done by glucose transport proteins (GLUT) that facilitate the diffusion of glucose into the cell (or they could run in reverse I suppose). These proteins are integral proteins located in the cell membranes. For example, in muscle this is GLUT4. GLUT4 is an insulin responsive transport protein.
The action of insulin (in the GLUT4 context) is to trigger actions within the cell to that result in more GLUT4 proteins in the cell membrane. GLUT4 (this insulin triggered GLUT) is present in skeletal muscle, cardiac muscle and fat cells.

My guess is that there may be some GLUT4 proteins out on the muscle because there is always some level of insulin in the bloodstream - but this would be a small effect on circulating blood glucose. However, the increase in insulin postprandialy brings more to the surface (note: I can't specifically recall that these are always present in some number, the great majority are certainly sequestered in vesicles waiting to be called into action).

Other GLUT proteins present in other cell types are not insulin dependent.

As far as I know, insulin is never 0 in a normal individual, though the fasting level would vary between individuals.

I assume there there is some normal baseline level for glucagon but don't know what it might be. You know that glucagon influences the breakdown of glycogen to release glucose into the blood not glucose uptake from the blood - so I'm not sure what you are asking about glucose getting into cells in the context of glucagon.

ETA: this is not the only action of insulin of course, just the one that you asked about.