Electrical – Altium – create a mirror image of a board

That's the Cypress FX2LP USB microcontroller (I recognize it because I use it myself). If you're using the Hi-Speed USB transceiver, then you should really go with a 4-layer board. Without that ground plane right below the top layer, it will be near impossible to get the 90 ohm differential impedance that you want for the USB D+/D- lines.

http://www.cypress.com/?id=4&rID=34128 flat out states that 4 layers is required. It also states that controlled impedance is required, but in my experience you can usually get away without it, so long as you carefully research your fab's typical stack-up and work out the right width, space, and height.

http://www.cypress.com/?docID=25406 also provides more info on calculating the width, space, and height for the D+ and D- lines.

4-layers isn't that much more expensive; Advanced Circuits has a 66 each deal for 4 layer boards that I use quite often for projects that use that very chip, as opposed to the 33 each deal for 2 layers.

In regards to your actual question...use plenty of bypass caps, as close to the pins as possible. If you split the bottom layer to have VCC and GND, don't have a trace cross the split on the top layer. Keep all high-speed signals on the top layer because the via inductance can kill what fragile signal integrity a 2-layer board has.

Hopefully I understood what you are trying to do.

You have to create a mechanical pair.

With a PCB open click Design Board Layers and Colors (Shortcut: L)

In the bottom left corner, you'll see a Layer Pairs Button. Click it.

Add your layer pairs together (like Mechanical 14 and Mechanical 30).

That's it.

Now when you switch components between layers, the items on the mechanical 14 will switch to mechanical 30 and vice versa.

I'll try and add some images and format this answer to be a bit more clear later on.