What is air pressure inside rubber birthday balloon?

I'm sorry, but I find this answer unsatisfactory. You are describing the act of inflation, while I am asking specifically about the scalar pressure value in an already inflated balloon.

I am talking about after equilibrium is achieved, you are talking creating differentials to make work. I am in agreement with you, when you blow into a balloon you increase the pressure inside. But, as you state, the immediate result is a change in the interior volume in order to remedy this discrepancy and achieve a static, balanced state--a state where this differential no longer exists, because if it did, the balloon would still be in the act of inflating.

I feel my position is more in tune with the principle of equal and opposite reactions.  There must be equal forces on each side of a point on a balloon not in the process of changing shape--the interior force pushing outward orthogonally, and the exterior force pressing inward in an exact opposite direction.  If these forces were not in balance, the balloon would be changing shape.  The potential energy stored in the elasticity of the balloon and put there by the act of inflation seems to me a separate issue.

I went a bit deeper into the search results looking for information about this, and I believe I have found confirmation of my original position.

Here is an interesting PDF on balloon physics;
http://www.eurekaeducation.net/files/physics/playing_with_balloons.pdf
Which is from a collection;
http://www.eurekaeducation.net/sub_files/physics.html

As described at the top of page three of the "playing_with_balloons" pdf, air pressure in a flexible container approaches that of ambient.  If a discrepancy exists between these pressures, this results in a change in the shape/volume of the balloon to maintain the equilibrium demanded from Boyle's law.

Think of the elasticity of the rubber as capable of storing potential energy.  When air is added to the balloon, work is done to stretch the rubber.  But once it is stretched, it does not require a constant greater pressure or influx of energy to maintain the shape--this would essentially mean free energy or perpetual motion.  As a rock lifted and placed on a table, the force of the rock down on the table & the table back on the rock is independent of the fact that the rock was once on the ground.

My brother has convinced me there is some greater pressure in bubbles and balloons, mainly because of way bubbles behave:

http://www.deepocean.net/deepocean/index.php?science04.php

But bigger the bubble, the less additional pressure it takes,proportional to 1/radius. And, if balloon left to settle, and outgas for days, it will eventually reach equilibrium, but in a typically inflated balloon there is some additional pressure.  How much (with balloons) still a source of debate, but fact that air goes from in to out over time means a pressure differential must be driving it, we think.