I don't know why people use the electron current flow (neg to pos). Not only does it have unnecessary sign changes, but it's not even "right" mathematically. The "current" value you use in calculations really isn't defined as the flow of electrons, but the flow of "charge".
Since the charges are negative, when you multiply the charge by the average electron velocity and integrate over the cross sectional area of your conductor, you get a current vector that points in the opposite direction from the avg. electron velocity. Thus, the current DOES flow from positive to negative, and treating it the other way is actually wrong.
The thing that seems to be confusing you right now, though, is the definition of voltage. First, voltage can only exist between two points--when you see a point in a circuit diagram that has a certain voltage (like a power supply connection that's labled "+12V"), that's actually the voltage between that point and "ground" (note that you can call ANY point ground, and the node calculations will still come out the same--its only purpose is to make the calculations easier).
Voltage itself is actually the amount of ENERGY (in watt-seconds) gained or lost for every coulomb of charge that moves from one point to the other (it's actually more complicated than that, but this gives the basic idea).
This is easy to think of if you compare it to vertical distance. If you take an object weighing 1 newton, and drop it, by the time it falls 1 meter it will have gained 1 joule of energy (1J = 1 watt-second). If it falls 1m and hits the ground, 1J of energy is released on impact (either bouncing the object back up, turning to heat, denting the ground, etc). If you lift it 1m above ground and drop it into a hole 1m deep, then it gained 2J of energy. If you throw it from the ground onto a 3m-high roof, then it lost 3J of energy during its flight. If you throw it hard enough that it reaches a height of 4m before falling back to the roof, then it absorbed 4J of energy at launch, lost 3J in transit and released 1J at impact. In this case, the energy is actually being "stored" in the combined gravitational field of the earth and the object.
In circuit theory, if a 12-volt battery pulls 1Coulomb of charge into its negative terminal and releases it from the positive terminal, that charge gained 12J of energy (this energy is "stored" in the electric field generated between the electrons that were moved and whatever atoms they were pulled away from). If it "falls" back down to the negative terminal through a conductive path, it has to release 12J of energy into that path (be it heating a resistor, charging a capacitor, energizing an inductor, turning a motor, etc).
This can be applied to a real circuit as follows:
Say you have a 12V battery with a 3-ohm resistor connected across the terminals. ohm's law states that a resistor will generate 1 volt of reverse voltage for every amp of current, and every ohm of resistance. Since that battery always has 12V across it (ie, it will freely give 12J of energy to every coulomb of charge that manages to pass through it), the resistor will have to generate exactly 12V of back emf (releasing 12J of energy for every coulomb of charge being forced through it). Otherwise, there would be energy magically appearing / disappearing, and a pair of points with two different voltages between them.
The only current that will satisfy this and, thus, the only current that can possibly exist in this circuit (equivalently, the current that HAS to exist in this circuit) is 4 amps (4A * 3ohm = 12V). This equates to 4 coulombs of charge, per second, being lifted up 12V and then filtering down through the resistor, losing its energy on the way. Thus, the resistor is releasing 4 * 12 J of energy per second as heat (48J / second), which is equal to 48 watts of power.
Hopefully that was somewhat easy to follow, and gave some idea of what voltage / current really are. In terms of what you'll see in books, the stuff above is basically a simplified explanation / partial derivation / qualitative proof of Kirchoff's voltage law.