exposing ports outside of SOPC

What you need to do is create an avalon master port and export it outside of SoPC builder. The easiest way to do this is to create a new component using the component wizard. Use the "Templates" to create a new Avalon Memory Mapped Master template. Because the component is not based on HDL, it will automatically export the signals outside SoPC Builder. You should create a master with a 32-bit address bus and a 32-bit data bus. It is your responsibility to make sure you address slave components on the bus correctly.